A friend of mine is on his 3rd GM Lambda CUV, Two Acadias and an Enclave. He got 15.5mpg mixed driving with AWD and 17mpg FWD. Pure highway he can push 22mpg, but most of his miles are around town carting kids, so 17mpg. That does not sound like an advantage over your truck!
If you want three rows of seats, then go for it. But economically it doesn't make sense. Maybe if you drove 30k miles per year on the highway.
I would strongly suggest the Ford Flex or Explorer with 3.5L Ecoboost over GM's Lamdas. Same 16mpg, way more fun!