Want to make life transition as smooth as I can for my dog

Hello all,
My husband and I have a german shorthaired pointer who is currently a year and a half old. While we have been at work, he runs outside in our fenced in backyard, and has a doggie door to the garage so he can come and go as he pleases. When we are home from work, he comes and goes inside the house and outside/to the garage when he pleases. He sleeps with us usually or wherever in the house that is comfortable.
Due to my husband and I separating, I am moving back in with family for the time being. My parents have a farm place with two other dogs that my dog has met multiple times and gets along with really well. He enjoys running and playing with them on the farm while people are home. The setup at my parents house is that the dogs have an outbuilding all to themselves with a radio, heat lamp and heated water for when it gets cold, bedding, and treats to play with. Attached to the outbuilding, my parents have part of the yard fenced in that they can play (The fenced in portion is about the size of the backyard my dog is used to). When people are home, they are let out to roam the entire farm place. They dont let them roam all day when no one is home in fear that they will get hit by a car on the gravel road near their house.
I am wondering what the best way is to transition my dog from an inside/outside dog to a full outside dog. I want to make the change as smooth as I can for him, and don’t want him thinking he did anything wrong. He will get just as much attention, if not more, after the move and will have two other dogs to play with all day instead of being by himself. The only huge change is the sleeping arrangements.

Please help!