There is nothing special about the generator propane hookup. You should be able to use it for whatever you want.
I recently built a propane fire pit for my deck and also installed a couple of propane torches (easyfirepits.com has all the odds & ends). They are pretty cool and are a great evening effect. However, they also suck down the propane like crazy. I have a 25 gallon propane tank that I have refilled three times in the past month.
Thus, I recommend to you... Go ahead and use the camper propane for a gas BBQ. Get a separate propane tank for the fire pit. That way if/when the fire pit consumes all your propane, you still have the camper's propane to run the stove & fridge. It would really suck to be out dry camping, see the fire pit go dim, and realize you just shut off your fridge.
Thanks,
-Eric
