First, welcome, Ricardo. The LT is an awesome bike, and you and your wife are gonna have lots of great fun on it.
Now onto your question. The tire size difference is pretty trivial, with the factory 160/70 tire giving a sidewall height of 112mm, and a 160/60 tire giving a sidewall height of 96mm. The overall tire height difference is 2*6mm, or 12mm. That's just about 1/2", and shouldn't cause any noticeable difference in ride, although it may affect your speedo/odo readings.
But I would be very concerned about the difference in weight rating. A tire with a 69 load rating (V is the speed rating) is rated to 325 Kg, or 716 lbs. A tire with a 79 load rating is rated to 437 Kg, or 963 lbs. That's a pretty significant difference.
I sure wouldn't ride an under-rated tire on my LT, even if I was solo and no luggage. The LT is a big, heavy bike, and tires are pretty damn important.
In addition, the Pilot Power
tires are a softer tire, meant for much lighter sport bikes where ultimate traction is a priority over tread life. Even if they do hold up to a two-up LT, you're probably only gonna get a couple thousand miles out of them.
Put it this way. What would you do if someone came into your shop and asked to have seriously under-rated tires installed. Would you have any concerns as to your own liability if something terrible happened?
I'd take the bike back and get properly-rated tires fitted.