After you do lots of homework and know it's the right change/addition.
How often do you have hookups while camping for AC and an indoor shower?
Is a north/south bed still OK if it has a partial wall on the fourth side?
"Not much more weight" - in comparison to what? With a TC, all the weight is part of the truck's payload. With a TT, the bulk of the weight will be in the truck's towing capacity. Also, with a trailer, it will have to be significantly longer to account for the lack of the cabover bed and have more floor space.
Not a large outlay of cash - how much is too much?
Loss of durability - the bigger the TT and the lighter the TT, the less durability you will have.
Potential issues - you are talking about having two campers instead of one. By default that means at minimum twice the work you have now.
Have you considered alternatives - like using tents for the boys when all four of you go camping. Adding a screen room to your gear can give you a protected space outside of the camper.
How long will the boys be camping with you? If they are hitting their teens, they may focus on other things like friends. Again, letting them use tents, etc, could open up a lot of space for you inside the camper.