If you want boys in white I would go with girls in white. For sure buy their shirts for them and have them pay you back.. You can make sure they get the right size and maybe you can find a womenís fit that you/they like. We use formal fashions; but there are several companies out there that Iím sure will do a fine job.
I would avoid letting them pick their own. Someone will always look a little.....inappropriate.
We went to black dresses a while back, and I love them. Kids bought their own for about 60$. Almost everyone was able to use the same dress for two years. No complaints and TONS of compliments.