Can you wear your baby in a sling/pouch while taking your 23 month old outside?
I know its hard but, they really need to burn energy.
Have you tried taking her to the local library maybe or going to feed the ducks?
Fingerpaints are great too, also water colors ummm coloring books of course or ohhhh stamps are fun. Yes, they're all messy just be sure to get the "washable" types. And they love to take baths anyways right
Just a few ideas.