JDFlow, I have made a few oatmeal stouts. I have used both instant flaked oats and golden naked oats with good success. Both add that silky/creamy mouthfeel you are looking for.
The golden naked oats are used like a crystal malt, and add a bit of sweetness and nutty flavor on top of the creamy mouthfeel. The grain is very small and you will need to adjust the grain mill to crack this malt. I made an oatmeal stout for a competition with naked oats that turned out really good and won me the trophy. This grain is not in every homebrew shop, though I am sure you could find in Seattle.
The instant flaked oats are very neutral and just give the creamy mouthfeel. With the instant flaked oats, I added to the top of the mash and just stirred them into the top couple of inches of the grain to help avoid a stuck runoff. You also want to use rice hulls with the flaked oats for sure-they get really gummy. I did a Rogue stout clone with flaked oats and it was very good, too. You can just use grocery store instant oats.
Either route, about 1/2 lb oats in a 5 gallon batch seems to have worked for me.
I think the Hallertau and 1318 will be great in an oatmeal stout.
Cheers, Tim