Jen just said what I was going to say. The only time I've ever used an e-collar on a cat is when they had a drain or line sutured in place, nothing to do with spaying. The cats I've had spayed bounced back, and I mean that literally, within a day of surgery. I've always kept them isolated in a small bedroom alone for a few days but there is no way I could stop them jumping up on the bed or into the window. I wouldn't cage for a spay unless the cat was sick in some other way. Also as Jen said, I keep a very close eye on the wound, checking for redness, irritation, building crust around the sutures, swelling, that kind of thing.

The only part I worry about, as I worry about it for dental cleaning or major surgery, is the anesthetic. However, since spays are relatively quick and easy, they may just use gas.

Can you isolate the cat in a bedroom? I just re-read your post and saw that you have young children. She will be groggy that evening and feel sore for a few days, so she can't be played with. I doubt if she will be irritable unless she is handled roughly, just a bit dopey and wanting to sleep it all off in a quiet area.