If you'll have a car I agree that Chestnut is a good option. It is in a second-ring southern suburb called Orchard Park. (estimated 25 minutes from HSBC arena or the airport). As previously mentioned the trails are not in good shape for running but there are many roads within the park and they are mostly free of snow. Running within the park will not get you to 14 miles unless you double up on some road loops. You can easily leave the park and run on roads and get to 14 mi. The roads are not snowy anymore and drivers are relatively safe b/c of the quantity of runners out there. The main entrance to the park is on Chestnut Ridge Rd (aka NY 277). You can run north or south down Rte 277 and take any number of side roads (some common road names are Gartman, Ward, Scherff, Cole, Newton, Powers.) There are decent hills (just about the best in WNY) in every direction from the park.
Cazenovia park is in the city (South Buffalo) but does not offer a lot of trails/grass or road loops. You can definitely park your car there but you'll have to travel far out of the actual park to get a longish run completed. Caz park is about 10 minutes from HSBC arena (search for the street named Warren Sphan Way).
Delaware Park is also in the city and offers your best option w/in the city. Delaware park is split into two major sections
(1) a golf course with a loop around it - rough guess 2 miles around. The loop is a paved road, and there is also a cinder path adjacent to the road for much of the way around. There is parking/entrance near intersection of Colvin Ave and Amherst St
(2) a lake w/ concrete and dirt path around it - about 2kilo around. There is parking near interection of Lincoln Parkway and Rumsey Rd. This section of the park also has a few minor trails/paths that can make it easily ~3k without having to duplicate any part of your run.
These two sections of the park are split by a highway (The Scajacuada/198). There is a bike bath and a pedestrian bridge that will take you from one section of the park to the other easily.
Additionally - when you are at the lake section of the park - you are very close to Forest Lawn cemetery (main entrance at intersection of Delaware Ave/West Delavan Ave). This cemetery offers tons of intertwined concerete roadways and minimal traffic. You can run in there easily for 60 minutes without overlapping anything. There are 2 other entrances to the Cemetery outside of the one previously mentioned.
Furthermore - when you are at the lake section of the park - you are connected to a Parkway system that has large grass streches along the roadway. From the intersection of Lincoln Parkway and Rumsey Rd (previously mentioned) you can go south on Lincoln Parkway, then there are offshoots onto Bidwell parkway and Chapin Parkway. If you go down Chapin Parkway you are only a block from the entrance to Forest Lawn Cemetery. If you go down Bidwell Parkway you will run out of grass at Richmond Ave. The grass on these Parkway stretches is still sloppy but getting dryer every day.
From the grass Parkways you can you run up and down tons of side streets – two major roads of interest would be Delaware Ave and Elmwood Ave. These are busier streets so you’ll be dodging people and may get stuck at a light or two. If you opt to run on these roads you will pass countless restaurants and bars. Buffalo has great food. A few places right near Delaware Park: Jim’s Steakout at Elmwood/Bidwell for a fast (sorta pricey) sub (get a Hot Blue w/ everything). Across from Jim’s Steakout is ETS (Elmwood Taco Sub). Along Elmwood there are at least 6 diners/greek diners where you can sit down and eat (including Towne restaurant which you mentioned, it is at the intersection of Elmwood/Allen) There are also at least 10 pizza places which will give you quality pizza and wings. Some ppl will tell you to go to Duffs or Anchor Bar for the best wings – but the truth is that you cannot go wrong at these other places, the price should be better, and the wait will not be as severe. The previously mentioned JP Bullfeathers is also very close to Delaware Park (just north of Jim’s Steakout and ETS and is well known for it’s food.
Back to running: Also in the neighborhood of Delaware Park is Buff State’s Campus which has a 400m track in it’s Northwest Corner. I have only been locked out of the track once in my life. Even if it is locked you can hop a 3’ fence on the home stretch at the wheelchair access ramp.
Back to the bike path that connects the two sections of Delaware Park – this bike path continues past the pedestrian bridge (previously mentioned) and goes along the Scajacuada Creek (this creek runs underneath the Scajacuada highway/198). The bike path is probably snowfree (I haven’t been on it lately) and offers another good option for running. At one point the bike path comes up to street level and hits Grants St. At this point you are very close to Buff State Track (it is just South of you on Grant Street). The path also continues further West towards the Niagara River. I cannot accurately describe how to follow the path after this point, but once you hit Niagara St (which runs along the Niagara River) you can find another offshoot of the path that goes along the Niagara River. You are far away from Niagara Falls but it is still a nice view. It is not really hard to get to along the path and get going along the river but it is not easy for me to describe in words here. If you are interested it is worth a shot. And you can always turn around and go back if you don’t find anything you like. If you take the bike path West towards the Niagara River you will end up on the West Side of buffalo. Some people will not run on the West Side b/c it is a mostly minority/Hispanic and there are elevated crime levels. It is not the safest neighborhood in Buffalo but I will also ad that it is not life threatening. I live on the West Side and run their daily.
Losson Park - aka Stiglmeier Park – this is in first ring-suburb of Cheektowaga but I cannot ad anything to the address that was already provided.
UB North Campus – in a first rings suburb (Amherst) just North of Buffalo. There is a 400m track there as well but I don’t know if there is access to it. There are lots of campus roads and also the Bike Path. I cannot offer much detail about the Bike Path but it goes for a long distance and I think would easily provide you with 14 miles (7 our and 7 back) of running distance. I just took a look at Google maps and it appears to me that the bikepath goes underneath Sweethome Rd just south of the intersection of Dodge Rd/Sweethome Rd. You can trace it’s path from there.