Tough, tough question.
I looked up the Florida statute which controls on the issue (can you tell I'm a lawyer?) and the current law states that your four year old is OK with just a seat belt, but the 4 month old obviously should be in a carseat. There are exemptions for school buses, other buses, tractors, motorcyles and heavy trucks, but not for taxis.
That said, you are not alone in this predicament. While the best, most safe answer is to bring along your infant carseat, if you don't have it with you then it becomes a problem.
The taxi will take your family to the zoo without a car seat for your little one. You can hold her on your lap. It's not ideal and it will likely make you extremely nervous, but it can be done. I admit that I have carried my daughter on my lap under very similar circumstances.
There are a couple of products you can buy for your little one to eliminate this problem. They are mentioned elsewhere on this board - I don't own any of them, but others seem to liek them. While I'm sure you can get them at other places, they are all for sale at Onestepahead.com. The first is the Tote and Go Portable Car Seat
. This is nice and small but only works for forward facing kids. The other is the Sit and Stroll
which is a carseat/stroller combo.
Aother suggestion is, if you are going to bring a stroller for the little one, you could bring along her infant carseat and pop it into a Universal Car Seat Carrier
. Then you'd have the car seat with you for the ride.
Days until my next cruise:
Renaissance R1, July 2000: Greece and Turkey
Radiance of the Seas, July 2002: Alaska
Golden Princess, November 2003: Eastern Caribbean
Grandeur of the Seas, November, 2004: Western Caribbean