Welcome to the neighborhood!
I live just down the road in Mount Rainier. We have one boy, turning 4 in September.
I'm new here, so I'm not sure how to suggest getting in touch -- I think I clicked the thing that lets other members send me e-mail. Please feel free to do so.
One thought: PG Pool is a great place to meet other families. Not cheap, but it's late enough in the summer that you can do a partial membership. http://pgpool.org/
And it's a lot more than just a pool. Drive by and you can see -- big lawn with picnic tables and grills. Huge kids pool, a sandbox under big shade trees. Sometimes they have bands play. Some nights it's open late and there's a campfire with smores. It's sort of a hippie country club.
Hope you enjoy Hyattsville!