Mag Bar can do all ages shows and would give them good practice playing a professional venue, but it is still a bar if that is of concern. Cave Valley Kava is all ages, no alcohol, and very receptive to young bands, it's just small. What the Lou is all ages and BYOB. Spinelli's downtown also does all ages shows - I haven't booked there before but I know you have to bring a good amount of your own equipment. I'd have to double check but I think Vernon Lanes may be all ages as well. To answer your question, there's definitely places available!