How does the sunroom work? Is it an extra room off the tent?
I would advise that it is a mistake to buy the biggest tent you can find, just in case the kids want to play, or it is raining. If you're not going offroad, you're probably in a van park, go to the games room, cafe, somewhere else. Take the kids, leave your wife with her book and a hot chocolate.
Bigger tents are just harder to put up and you can spread your clothes over a wider area. My old camper had a 9' tent and an extra room. The 9' tent allowed us plenty of room to have a set of bunks and stuff on the floor. The extra room only went up if we stopped for a week.
No one spends time in their camper. No one. you get dressed in there or you're going to sleep, or putting the kids down for a nap.