A house is a house.....

We are living in our third house in the past 10 years. The first one was a three bedroom ranch that was small but worked for us when we only had little toddlers and babies. We finished the basement and we really liked our house but the layout was kind of choppy and small for hosting. We then built a nice big house with all the bedrooms upstairs and plenty of room for hosting. We didn't really like the mortgage payment on that house and I really prefer old houses so then we moved into the house we are currently living in. It's great except that we have 3 girls, 1 boy and only three bedrooms. We have an extra room off the kitchen which we use as a playroom that we could make into a bedroom but then we'll lose our playroom/extra room and I don't like having bedrooms on the main floor. So our dilemma is, add on off the back of our house, we have a flat roof that we could add onto and make two extra bedrooms and a bathroom upstairs, giving us a master bath and bedroom upstairs and each kid their own room. Or we could redo the room on the main floor but then all the toys would need to be in the kids rooms and we would be on the main floor. I know that they won't have toys forever but it would be nice to have another "room" for the kids to hang out in that we can keep an eye on and I don't like the thought of kids hanging out in their bedrooms with friends all the time. The last option is, we move into something that doesn't need remodeling and fits our family better. We go back and forth over these options and it's driving me insane! I'd love to hear from some people, what are your bedroom/family room/play room situations. We maybe could finish our basement but it's wet, scary and full of bugs. It's flooded before so I hate to think of putting carpet and drywall down there only to have it get ruined. Do your kids share rooms? Do you have a bedroom on the main floor? Do you have older kids that hang out at your house? I'd love to hear your thoughts on this!
Thanks!