awwwww they're adorable!!!
lotus was my first female animal (well, when i found her and her brother, i was still under the impression that nena was a dudette, but i know better now), and so she was my first experience with spaying.
neutering is not nearly so intrusive. but spaying is entirely different altogether. and i know thta it's for their own good and that it's the responsible thing to do, but i feel so horrible when i see them all drugged up not knowing what happened.
when lotus was spayed, she was just low-energy for a couple of days. and even though her brother was still a baby too, there wasn't really a problem with her ripping ehr stitches out or anything.
frankly,i don't really think she was feeling well enough to go tearing through the house like she normally does. so i think it definitely varies from cat to cat.
just give them lots of love (and maybe a few extra treats here and there), and, like everyone said, watch those wounds! with little girl kitties, especially regarding the placement of the incision point, it's really easy for those to get infected.
so if you see anything on either one of them, it's off to the vet! and also, remember that they'll be really groggy from the anesthesia. so try to keep them off of high places until they start acting normally again.
but i'm sure everything will go just fine. they are too cute for complications, lol

good luck!