Trailer GVWR is probably a good starting point but really you need to weigh it fully loaded to know for certain. Unless you are obsessive with a family of 5, you are probably going to use all the cargo capacity of the trailer.
As others have said, if your payload really is under 2000lb, you are going to be limited to very small 5th wheels. Let's say 500lb for 5 people plus 200lb for the hitch...that leaves you only 1300lb for pin weight if you put absolutely nothing else in the truck and you have no after market add-ons (such as running boards)...Assuming 20% pin weight, that leaves you 6500lb fully loaded for the trailer. If you carry firewood, spare gas, generator, etc... in the truck, it reduces the trailer size even more.