Positives and negatives depend on their ability. My kids have won nationals before but it's a different animal at that meet. Districts and regionals mean nothing. There are areas in New York where incredibly talented kids don't even advance to nationals bc there district is so tough. Meanwhile you see quite a few districts who just aren't very good and those kids advance. I watch those kids get crushed at nationals and it probably leaves a bad taste in their mouth. So check your kids times and have them run in meets and districts but unless they are in the top portion in the USA don't bother with nationals. It will break their hearts when a bunch of twelve year olds runs the first 800m of a 1500m in 2:18-2:26. I've seen lower than that as well.
Keep it fun at that age because today's losers are tomorrow's winners. I never pushed too hard and we had some crappy years before they really got going. Trust me, no amount of pushing is going to make a kid want to run or great at running. They have to want to do it. Please respect their views on the matter and don't become one of those jerk parents I just saw today at an aau meet who scream and stick their fingers in their kids chests. If the kid wants to run, run, but don't put that pressure on them to be great. Make it competitive but fun right now. Worked for us at least.
My sons went over to the kid after his dad screamed at him and told him how well he ran and the poor kid burst into tears saying how he tries hard twice a week at practice and then his dad expects him to run way way better times at the meets. Meanwhile most of these kids that poor kid is running against run at least four times a week (my kids included) so why is he being judged by a guy who isn't even smart enough to realize that the kids in front of his kid are trained to do that and stop expecting miracles come the day of the meet.
Just really sad watching some parents overreact and act like bullies with their kids. So again, just let your kid have fun and take it is far as they want to take it. Explain that to be great requires work and if they are willing to work, good things will happen. But don't push if they aren't ready to commit. Let them be young and enjoy running. Don't take the fun out of it for your kid like that idiot did today. Good luck either way!