I would guess Lawries Caravan to be in the 800-1000 lb range, irrelevant.
Since the brakes on the 36 were adequate at best, brakes on the trailer would be a must.
I've never been a big fan of surge brakes, but they do work with light loads like you want.
Electric brakes are better, but of course would require you to wire that all up, and are you 12 volt?