1. Wheelchair passengers usually get escorted to the front of the immigration line. If your parents are not US citizens, they will probably get priority handling in the non-citizen line to get photographed and finger printed. If they don't speak any English, they probably need help filling out entry and custom forms. Hopefully someone from the airplane can help them do this before they arrive at LAX. 3.5 hours is generally enough for this transfer.

2. There is bag re-check at TBIT right after custom before leaving the sterile area. If they are on the same ticket to SFO, most likely their bags will be tagged to SFO. If that is the case, they can just drop it off at the re-check station. If their bags are tagged only to LAX, they need to see if there is an Alaska rep at the re-check counter that will help them check in. I'm guessing there is no Alaska rep at TBIT - if that is the case, they will need to take their bags to T6 to check in with Alaska. The takeaway here is make sure bags are tagged to SFO at the first check in.

3. They will be pushed from TBIT to T6 check in thru the sidewalk on land side. There maybe a hand off somewhere between the two points for different handlers that are assigned to particular terminals but they will make sure your parents get there.

4. You can meet your parents at the TBIT arrival public waiting area. That's where they will emerge with their wheelchair handlers. Your same day boarding pass can only get you inside secured zone but not sterile zone so you need to wait for them land side to meet up.