DEFINITELY buy the Bob stroller carry bag! You wouldn't want it to get dinged up by the luggage guys.
Are you travelling solo? If so, I would check the stroller and carry your son in a sling or wrap or Baby Bjorn. If you have someone else travelling with you, it's a snap to take off the wheels and put the Bob into it's carry bag, once you try it out a couple of times at home.
Most airlines do not consider strollers and carseats as part of of your luggage count. You can also gate check your stroller so you can have your stroller in the airport. Then when you get to your gate, just ask for the gate tag then leave your stroller at the bottom of the ramp. Then when you land, they will have your stroller waiting for you outside the plane doors. Also, if you check in your stroller or carseat, most times when your luggage comes off the plane, they will hold it for you at the Customer Relations office, or just outside of it. So check there first before you wait forever by the carousel.
Now that we have a 4yo and a 2 yo, we just check in our Bob and bring a cheap umbrella stroller to wheel my 2 yo around in the airport. So you could do the same. That way you have the comfort of your Bob during your trip and just have something cheap and handy for the airport. Again you can gate check your umbrella stroller.
Have fun on your trip! My kids have flown from S. Cal to S. Dakota and to Austin, Tex with no real problems. Our next trip will be a 3 day drivin trip from S. Cal to S. Dakota at the beginning of May. Pray for my sanity!!!!