Check out the youth programs in your area. Generally each town (Vienna, Great Falls, etc.) have youth teams as young as K-2 playing against other town teams in Northern Virginia Youth Lacrosse League. Honestly, for a rising 2nd grader this is the best place to find a team environment. Below is a link to NVYLL page with links to the team websites.
http://www.nvyll.org/ClientClubs.asp?org=NVYLL.org