Hey Miranda,
Be involved with the other kids. I'd kick start a game of street hockey or freeze tag or something and get to know who is who.
Just because you're one of "the moms" doesn't mean you can get more involved. You live in that neighborhood. So do your kids. Your presence will definitely detour some of the bullying. Watch for it so you can see for yourself.
You don't have to spend every single day outside but you can definitely spend a few afternoons a week with them...maybe for an hour or so. And don't announce it either - just waltz outside and start playing with your own kids and let others join in - 2 little boys are not going to run an entire neighborhood. Step in and show the other kids how to handle mean kids.... that'll take away some of their intimidation.
If the 2 boys cause trouble, send them home. If it happens again, send them home and escort them and let their parents know whats going on and that you'd really appreciate a little more supervision since their kids are hurting others.
Thats just what I would do. In our neighborhood there are kids everywhere and we live in a lower income, not-so-nice-and-safe area. We chose to be here for several reasons, mostly to help out where we could. We knew it would create situations similar to yours with our own kids. I've handled many a bully. The most important thing is to get involved and make it stop, because bullying is absolutely unacceptable. I think recent news reports can prove that to everyone.
Best of luck to you guys, stay strong!