Yeah, and even if you don't have a boarding pass, some lounges can give you a "Gate Pass" that will get you through security. I've done this with both the CO Presidents Club and AS Boardroom when incoming flights I was meeting someone off of were running late. Could be such access is at the discretion of the lounge receptionist, but I've never had any problem.

You, however, will most definitely have a BP via home check-in, so moot point.

I did however once have a TSA agent deny me entry at the security checkpoint for NW and the South Satellite because my ticket was for travel on Alaska. I tried to explain that I could get over there anyway via the AS/NW Shuttle Bus at Gate C2 or I could take the connecter train from the North Satellite, so it wasn't like such access wasn't allowed. Fell on deaf ears. Not the brightest agent. In any event, if that happens, just go down to the North Satellite checkpoint and take the connecter train to the South Satellite station, then off to the South Satellite from there.