Just thought I would share...today until 4/5, Zulily has some good deals on formal wear for little ones! They have cute dresses for FGs too!
My BM/mom of our RB sent me the link since we couldn't rent him one because he's too little (will be 19 months at the wedding) and they only sell his size (for like, $70!) I think we're going with the one at the bottom of the page with the silver vest, since our dads and FI are wearing silver. Can't beat $24.99 for a full tux!
http://www.zulily.com/e/la-sun-040612.html?pos=0ETA: I believe you have to create an account to view them.