Young Boys in the Wedding Party

Hi,
I wanted some advice on what to do with our 6 nephews (besides the 2 Flower Girls) who are going to be in the wedding party. My FH is not wearing a tuxedo, black suit instead, and their moms don't seem to want them to get too dressed up. (One mom asked if her son has to wear a suit...)
Any good places for suits/ties for young boys? (ages 5-11) Any thoughts on what they can wear?

Thanks!!!