I am glad to see another family interested in fiberglass trailers.
floorplan B with the optional gaucho front bunks will work for a family of four but there isn't much extra room for everyone to be milling about. I think the front bunk is rated the highest of all new models (200 pounds) and the beds are 77 inches (6 feet, 5 inches) long. The Casita's that I used to rent had a bunk rated to 80 pounds but maybe that has changed and it is probably conservative for protection of the manufacturer against kids bouncing on them and such. The other brands with bunk beds are fine options as well but I don't know the bunk weight
capacities. The floorplan A option has dinette and bigger beds fore and aft which might work if the teenagers can share the bed.
The headroom when standing may be an issue. I am 5'10" and easily clear the ceiling in my Escape
, though I don't wear shoes inside. Some of the other brands have more standing head room.
My two kids are still in elementary school and I expect we will be using the trailer for many years to come. A small tent is a great idea as an add along if the situation allows it; we bring one to play in. Here is a link on family friendly floorplans:
Family Friendly Floor Plans, A discussion of trailer models suitable for 3 or more people
Best of luck and happy hunting, a good match is out there somewhere.