Adapting to Changes

Recently I have had to make some changes in living arrangments waiting on my house to be available. In the interim our 4 month old Roscoe has been at my sister-in-laws in her back yard with her dog. He adores Belle and has adapted quite well to the situation. I am even told Belle has adapted along with being protective of him. My concern is bringing him to the new house, which does have a huge back yard, all by himself. He now has the company of another during the day and I don't want to confuse him anymore than he probably is due the the recent circumstances....any advise. Thanks for this forum...it is a great place to find answers without evening asking!!