it will look the same. visually GB does not look much different than froyo. its considerably better at killing unneeded background processes,among other things,but if you put a phone running froyo and one runnig GB next to one another youd be hard presed to figure out wich was wich without lookint at the android version in settings/about phone.
if youre looking for a sexy new UI or newer sense version,its not gonna be the stock GB OTA.
youre much better running custom roms if you want your phone to have a new look and feel.
ive noticed this same exact phenomenon on the TB forums... people for some reason have an exceptionally high,overly estimsated expectation of what they think the GB OTA will be. i dont know if its just GB hype in general,or the fact that its been so long coming,but most of these folks are going to be exceptionally disapointed when it hits.
fear not,you will be able to flash the OTA in clockwork recovery before its pushed to phones. then you see how its not much different than the froyo you have,you can encourage your sons to root before its too late