I think it is a great idea to offer bows to match the dresses....let me know when you have them so I can order to match the dresses Tini got (which are beautiful by the way!).
Definately make sure to give people the option to select either the mini barrettes or the latex bands. I would also suggest selling packs of the elastic bands as well....you can never have too many of those and it would be a nice thing to be able to order extras.
Here are a couple of links to some bow packs I won on ebay...just to give you some ideas of what others are doing out there....
http://cgi.ebay.com/ws/eBayISAPI.dll...e=STRK:MEWN:IT http://cgi.ebay.com/ws/eBayISAPI.dll...e=STRK:MEWN:IT
Hope this helps and good luck.