OP--You know you don't have to get your checked bags, right? To me that is the best part of Magical Express--not having to deal with my checked bags. Pack what you need for the first night in your carry-ons and let Disney deliver your checked bags. They will even hold them at the resort for you if you don't want them delivered right away.
Also, the bus routes are not set in stone. CBR may sometimes be the first stop, but I can attest to the fact that it isn't always first. Planning on a 2 hour travel window is a good place to start. Hopefully it will take less.