Nice little site there Bruce! I only checked a small part and seems the guy has a little error. He states: "After you choose which course, if you have Cid or Tifa in your party, they will sometimes ask to ride. Not even I, the Chocobo Sage, know why. I do know why they're the only ones who ask."
This isn't entirely true. I've had Vincent ask to ride also
Regardless however, a nice little site for anyone who needs more info on the Chocobos in FFVII!