Dont forget the Air France bus has to go to terminal 1 and pick up / drop off people after it has picked you up at terminal 2B plus the only every 30 min departure... It then has to stop at Gare de Lyon for more drop off / unloading of luggage. Sounds risky to me. I suppose you will have a better idea once you have collected your luggage. I would consider a taxi or if you know how to get to the RER station and buy your tickets quickly that might be an option.