I do exactly what you describe. I have a 20' boat weighs in at 4500#s with a half a tank of gas. A few times a year my wife pulls it behind her Tahoe, while I pull the TT behind my truck. Tahoe is an 2003 with the 5.3 and pulls it pretty good. We learned that we only bring boat and camper together a few times a year bc it gets really expensive and a lot of work when you bring both the TT the boat and two tow vehicles. Lots of prep work involved there!
And at least where we live/boat, 4x4 is not necessary on boat ramps if you have common sense. I pull the boat with my 2wd truck with no problems. I spray my trailer bunks with a spray made for the boat to slide right on and come right off, which makes loading/unloading much easier with 2wd.
Next time we upgrade the Tahoe we will probably look for something with the v6 for better fuel economy for all the running around she does throughout the year.