Stick with the stock size for primarily highway use. Your use description fits the Michelin LTX M/S profile well. For those of us with 16" wheels, the 275/70R16 114H was designed specifically for the LC/LX and it is a superb fit.
With the 18" wheels, the Michelin Cross Terrain was the preferred tire. This has been discontinued though some places still have them in stock. The replacement is the Michelin Latitude Tour HP and it has an H rating. It is an improvement over the Cross Terrain and LTX M/S, but also costs more. If you can find a clearance price on the Cross Terrain (check tire rack), go for it.
I am a big fan of the LTX A/T. I had them on my F150 and it was outstanding... Quiet, great in ice and snow, and at 75K miles still had half the tread left. The A/T2 looks to be an improvement. If it is available, I would not hesitate to recommend it.
Costco is a great source for Michelin and BFG tires. They get the premium lines plus all their techs are certified by Michelin. They also use nitrogen to fill the tires at no extra charge. We do not have Costco in AR (for some reason home grown Sams has the market); however, I joined Costco on a trip to Dallas and got some of the last LTX M/S H rated tires available (discontinued) and they did a fantastic job. The balance is perfect and the LX drives like it is new. Amazing. If you get tires at Costco, they have $70 off a set through this weekend. Sams prices were slightly better than Costco, but the installation at Costco was worth the difference.