Brandylouwho is exactly right. The one thing I would add is put your stroller in a bag. We didn't have one last time and were able to get a large plastic bag from the airline at the gate to wrap it and protect it from grease, damage etc. This time I bought a gate check bag from Target.com for $12.99. It zips up and has a carry handle and a storage pouch for the bag when you're not using it. It is a little thin but it should do the trick.
We do the same for our car seats so we have quite the load at the gate, 4-5 carry-ons and 4 car seats in bags and a stroller in a bag. Just thinking about it makes me tired. At least this time I think I can put the low back booster seats for my older kids into one bag.