I haven't had too much trouble at dog parks. When my dog was younger, <1 year, she was constantly being bullied by the male dogs, she is a ball of energy (Ridgeback/Boxer mix) and that usually gets the dogs irritated I guess. She started to hold her own, and things became normal after a few uncomfortable situations at the parks. I had to bitch smack some owners, since most are retarded and inconsiderate.
I think parks are a great idea, I know Lucy loves running with other dogs. Let me know if you want an easy going, hyper dog to play with your pup.
PS, lucy was constantly humping my brothers Doberman, which is now 90lbs. lol