Hi D.,
When we evacuated for Rita, my daughter was 18 mos. She is now 3 and I have a 7 mo old as well. So, I'm packing up too!
I would make sure you have your pack n play to provide a place for your baby to sleep and to play. You'll want to make sure you have plenty of binkies (if you use them). You'll also want to bring a bottle washing kit--a plastic tub, bottle brush and soap. Dont forget the drying rack as well. I would bring 2 days worth of bottles, so you're not washing bottles all the time. If you're lucky enough to be sheltering at a relative or friend's home, you can use their dishwasher to wash bottles--just be sure to bring the basket.
Also, make sure you have PLENTY of changes of clothes. I quickly found out that the cheap diapers I bought leaked. So we had to change her a couple of times. Also, be sure to bring a light towel for sopping up a wet car seat, etc. It also makes a good cushion for laying her down in the car to change her diaper. If you use a special laundry detergent for her clothes, you'll want to bring that as well.
Lastly, bring toys and books for her. She may not be using them now, but at least you'll have something to play with her while you're sitting around. =)
Good luck!
A.
P.S. I would evacuate early. I plan to leave on Monday even if there is a small chance it's going to hit Houston. I don't want to be sitting on 45 for hours on end again. It took me 23 hours to get to Dallas from Houston. My mom's car broke down along the way too. So..the point is that you don't want to get stuck on the side of the road with a 3 mo old in 100 degree weather. ]
P.S. Don't forget your stroller.