R.P.
you CAN do the zoo and take a double stroller or a regular stoller for the baby and a wagon that the girls would be able to sit in for them if they get tired and nap in the car after you leave. its not that big of a deal at all. You can also take her to a teeshirt shop before hand and get personalized teeshirts for the birthday girl and her best friend and maybe somewhere that she can paint an animal