I'm so sorry to hear about the kitty, how sad!
I would definitely keep your kitties inside full time after Buddy & Dollie arrive. Perhaps in time with training you will be able to make them understand that cats are allowed in their territory, but personally I would never risk it after you've seen what they can do and how it only takes a second!
Hopefully, you don't have a lot of neighborhood kitties that like to wander through your yard. But if you do, you may want to consider buying a 10'x10' chain link kennel (Home Depot or Lowe's usually have them for around $200 or so) to put in the midst of your yard for a little while. If the dogs are inside this secondary kennel within your yard, it will keep them from hurting neighborhood cats while the cats figure out that there are dogs on duty now and that they'd better find an alternate route through the neighborhood.
It's great that the dogs are becoming so affectionate with you! That will make their transition so much easier. It sounds like you are handling their move really well.