I think the THV's are going to be WAY more comfortable for 6 than they will be for 8-9. With 6, everyone has a real bed; with 9, I think you'd better really take a long, hard look at what kind of sleeping arrangments 3 of those folks are going to have. Two of them will be on a sleeper sofa and one in a sleeper chair. (In OP's case, if some of the kids sleep with the parents, that's better -- but note that both the master bed and the second bed are queens...not kings.)
Also, it matters how many family units you have. Don't forget, you only have two bathrooms and the second bathroom doesn't exactly look spacious.