Are your chams "latrine oriented"? Many chameleons are. It's a term used for animals that "poop outside their camp", or at least poop in the same spot each day.
Guido is. He lives on a miniblind in a bay window in our home office. He now poops in the shower. But before that, he was latrine oriented, and always pooped exactly in the same place, within about a 12" range. We would just put double layer of paper towels on that spot, and replace the towels afterwards. He basically pooped at the same time each day, as well.
It was quite comical, actually. After he warmed up in the morning, he would travel down his miniblind, across his grapevine, onto an exoterra vine, and out to the "latrine". Do his business, wipe his butt on the exo-terra vine, and head back. THere was no way he was going to let that mess in his habitat.
Anyway, if your chams are latrine oriented, then free roaming should not be a big problem. Your greatest challenge may be keeping the cham hydrated. As for feeding, worms and crickets go in a TALL plastic cup that the crickets cannot escape from. The cup is hung in the same place each day, near a perch where you chams can sit and eat out of the cup.
ALSO: you may wish to chameleon-proof, as in baby-proof, the area. to me it seems that chameleons are very curious, and also that they will try to eat specks of things they come across that could be quite harmful. And they can't grasp smooth surfaces, so could fall off the edge of a bookcase, etc. A strip of masking tape along the edge of a smooth surface may help for gripping.
