My kids loved Boma too. In fact, they loved it so much, when we go back for my son's 9th birthday in January he has requested his birthday meal to be at Boma. Why do they like it? This is exactly how he and his 6 year old sister explained it: #1 - we don't have to wait for our food; #2 - we can take just as many chicken nuggets, or as much mac & cheese as we want, then if we want more we can get more, but we don't have to worry about not finishing what the waiter brings us.
My son is VERY picky, but he even said he may try some of the soups when we go back (this is a HUGE step for him).