I'll preface my post by admitting that I'm 32 myself.
Having said that, 33 really is that old. You might not feel like it, but try to remember what you thought about 33 year olds back when you were 18-20. You probably thought they were kinda old. Nothing's changed man, the only difference is that now you're the 33 year old vice the 20 year old.
Besides, how exactly would you expect to get along with a team of 18-21 year old college kids. Other than running, what would you talk with them about? How their 401k is doing? How about mortgage refi rates? Face it, collegiate running is a young man's sport, so leave it to them. Doing it in your 30s is just kind of sad.
By the way, that is a nice 10k PR. You should be proud of that.