It's the weekend and you will probably get more replies on Monday. I have not ever had more than one dog but the usual suggestion is to introduce the dogs on neutral territory first. A walk together maybe. Leashed at first then maybe at an off leash place. I'm guessing but I think I'd split the pair for the first time you bring them into your yard and then your house. Wait, more ideas will come. I hope it works, great for you and them.