Let's see....
I think there is a bag you can get for gate checking the carseat (yes, definitely bring it - baby will be too little for the stroller without it, and like you said, you can use it on the plane if there's room). I will say though that I never bagged my carseats when checking them at the gate, and had no problems (though I've read that they can get pretty dirty sometimes). It just seemed easier/quicker not to bag the carseat...I knew I could wash the lining if necessary.
Taking a little one to Disney...
1. Be sure to take a couple of outfits to the parks each day. We took DD when she was just under 3 months and the first thing that comes to memory is that she had "blow outs" at each park!! She was just at that age (and possibly the wrong diaper size???) where they happened a lot. Fortunately we had plenty of outfits with us. Even more fortunate, we had a washer and dryer!
2. In addition to the stroller, we brought our Baby Bjorn and used it a ton! She spent a lot of time in the Bjorn....looking around, riding rides, sleeping. It kept her cozy and comfy, being close to mommy and daddy. Though I should note that we were there in late Jan.....so we didn't have to worry about heat.
3. Be sure to bring a baby blankie, even if it's still hot out - for blocking the sun in the stroller, covering up in an air-conditioned ride, etc. Layers are always good with babies.
4. I'm sure you've read about them, but the baby care centers are really nice. A nice, quiet place to change baby, feed baby, cool off, etc. Although I will say that they are not always that convenient to get to when you need them. We often hit them on the way in/out of the parks for a diaper change and feed, but also had to do that in many other places around the parks. There are plenty of quiet little nooks where you can feed the baby in peace.
5. Pack plenty of wipes and diapers - they are pricey down there if you have to buy them (even offsite at a drugstore or grocery store). I nursed, but I'm sure the same goes for formula.
That's all I can really think of. It's all pretty obvious info I'm sure.
Have a great trip! I have a lot of sweet memories of being at Disney with my little girl!
