Thanks everyone, your post are making me feel better
I figured getting them done at the same time would be better for them AND me. That way one wont bother the other. They normally sleep in bed with me (high bed) but I'm planning on sleeping on the couch and setting up a pallet on the floor next to me, but knowing the they'll want to just be on me constantly.
I work from home so I'll be able to be there with them afterwards. If I had to predict how they'll react after the surgery, Olive will be sluggish and sleep a lot, Lily... haha I have a feeling Lily will be the drama queen and cry a lot. When Olive got her shots she never had soreness or whined, where Lily acted like she was bruised all over for a good two days.