My opinion is that that's a whole lot of trailer to learn to tow with. I've got you beat by one year and have towed our 23SS Hybrid and now our 2604 TT. I noticed a difference and surely wouldn't want to even think that size.
Suggestion would be to spend some time...lots of it... online looking at floorplans in the 25-27' range. Some do have a front bedroom and a rear "bunkhouse", usually something like a double size on the bottom and a single above. Usually there is a curtain you can draw closed. For starters, you might look at RV Wholesalers. We've bought 2 units from them and they're good to deal with and no game playing....but the benefit for you right now is that they sell a ton of different lines. You can just sit back and look at a lot of floorplans without having to drive all over the place.
You didn't mention what your tow vehicle is and the specs on it. That would help a lot for getting good guidance here.
I think it's great that you and your son are getting into something like this. We have a son with a lot of challenges and health problems...he absolutely hates camping! The only time he will even think about it is our yearly trek to FL for spring training. Baseball fixes everything. One good thing is that we get a break from him. Another good thing is that he gets a break from us, so it all works out. Do wish he would join us more often, but he'd rather be home for catching all the baseball games he can and tending to the doggies. Everybody is happy.
Please let us know how this search is coming and for sure the info on your tow vehicle. BTW.....do not believe everything a salesman tells you....sometimes it's not quite the truth.