Here's my suggestion...
Take the Snugride w/out the base (check that in a bag; or use the carseat without the base for the time you are away, it sounds like it won't be a long trip) and see if there is room for your carseat as you are boarding. Usually, they will try to accomodate you. If they don't have room for her carseat, you can simply gate check it. If there is room, perfect.

I am sorry for your loss....

And OT; Southwest sounds like such a great airline for traveling with kids!

Also, when you read the CPS training stuff or online info, you can learn more about the possible dangers of flying with a babe in arms. There are real risks, but nothing better or worse than the rest of life's risks...

I do agree with a PP, that putting a 2 mo old in a seat would depend on the kid. My dd loved her seat; my ds never did like being in the bucket and would have made a whole plane full of people very, very uncomfortable. But no doubt about it, if you put absolute safety very first, children are safer fastened in.
HTH! Meg
Follow Mothering