For my 50th we are flying CW Brussels->Heathrow->Los Angeles->Honolulu (& back) early August '10 on one (paid for) BA booking (thank you FT).
I believe I can check in for the first two flights (dep 10.00 & 12.00) at the same time (24h before first flight), but we've got a Layover at LAX (so we can visit the best Bloody Mary bar in the world*). The final flight LAX-HNL (with AA) departs 19h after we land at LAX (34h after first flight).
Can I check in for this at the same time? (Is it via the BA site or do I get automatically linked to AA?)
If I can't check in for the third sector, can I do this when I get to LAX at a check in machine or is there an easier way?
Welcome to FT, am not able to help you, but see you have had loads of people that can help. This is the best forum to get onto and get the most up to date information from the experts, and you will have many days of fun reading all the threads and comments, and pick up lots of tit bits. Enjoy your trip. Have not been to HNL since 1980, would love to go back one day.^

* the best we found on our RTW 2 years ago (around the world in 18 days)