I got Monroe load shocks see:
I know two others that installed these this year and are happy all towing big heavy caravans.
At $120.00 and real easy to install they are hard to beat. Air bags and local standard shocks will be more $$$$.
My rear shocks @ 118000 klm were shot.
We carried on and replaced the front struts and HD Anderson springs front and back.
Suggest you try just the load shocks they will probably do the job for you without anything else.