I've done it in the past (last November) and have never had a problem. Getting a second parking pass isn't a problem either. As long as you are within the occupany of your room you are OK. Last November after a cruise my DD and SIL stayed the day with us at the BCV before their flight that evening. I went to the front desk and got room cards for both of them so they could use SAB. We were booked in a studio and it was just the 2 of us, so adding them for the day was OK.
However, this August I was staying at the BLT and when checking in I noticed my granddaughter was not on the reservation. It took 30 minutes to cancel and rebook my reservation so they could add her. Now I don't know if this was a BLT issue, or a drawback of the latest computer upgrade, but it was a pain in the butt and I did write to the MS satisfaction team about how complicated it got, along with other negative issues that occurred and they apologized for the check in problem. I would be curious to hear if anyone else has had an issue lately.