I got two fanny packs for my 10 and 6 year old girls from a site called shopbags.com. They have a bag called the Everest Mini Waist Fanny Pack, I think it was about $7.00, and they worked perfect for them, we didn't need to tie them in knots or anything, perfect size. Every day they carried several snacks in them and sometimes their autograph pens. They don't hold a lot but they were just right for what they wanted. They never complained about having them on.
I also got a bag for me as well, just a compact organizer bag that has several different zipper compartments that worked great for holding the maps, camera, and various other junk we seemed to need each day. I ordered it in black and my husband carried it as well....not very "purse" looking, just a nice travel bag.
Hope this helps!