1) Mobility is going to be an issue with a very active 2.5 year old. I think the Kolcraft Contour Double Stroller and the Gypsy Mama Water Wrap are going to be must haves at our house in order for me to keep up with two of them on the road and in the water! The stroller has lots of options for changing seat positions so you can effectively put a child in time-out while on the road! (I walk with moms of two children and let me tell you, THAT is an awesome feature!!!)
The seats can face each other, away from each other, both front, or both back. Perfect for time-out on the go.
I can definitely see myself chasing Jessica around the pool while wearing the new baby in this swimsuit material wrap!2) I may also need to pick up some more cloth diapers/washcloths.
3) Definitely more soap and other consumables.
4) Clothes. This child will be born in a different season and may be a different gender. I have some gender neutral clothes and some heavy and light clothes for all sizes, but I may need to flesh it out a bit.
5) Nursing bras tend to wear out after one child from all the opening/closing, expanding and contracting, and later on tugging on by your child. I think new ones will be in order.
6) We have an infant car seat, but eventually we will need a convertible car seat. Jessica needed to stay backwards for a while because she was so lightweight, but she needed a convertible car seat because she got too tall for the infant car seat.
7) And then there is preparing Jessica for a new sibling. At some point before or after this baby arrives, she will be potty trained. At some point before or after this baby arrives she will also move to a big girl bed, which is all ready minus the mattress pad. However, the thing I have thought about the most is that I would like to give her a doll when the baby arrives complete with a diaper bag full of all the things that are in my diaper bag. (I think it will be absolutely adorable!)
Overall though, there are very few immediate essentials for subsequent children. Most of it is not truly essential and just comes down to how you can keep up with them without loosing your mind!