I'm not sure of your trailer size or space but how about a 4WD Touring tent in the 9ft Model ??
We had one of the original Southern Cross ones pre-kids....
Single centre pole, Canvas, internal floor space 9x9 and about 7ft High in the middle....most have a attached vestibule awning now (ours didn't)
Set up time about 1-2 mins incl awning....centre pole, and 4 pegs and another 2 poles and 2 pegs for the awning.
They are about 15kg and now the trailer issue.....about 800mm X 800mm and 120mm high packed size.
I think oztrail make a copy of the Southern Cross
about $300 (ish)
Only real problem with a canvas tent or even single skin synthetic tent is they can wick a little if you pack it up wet to setup later that day......hence the fly seperate is a good option
Cheers