Hey Bambi,
You'll be alright! I had botox without anesthetic and it's a very quick and simple procedure. 10-15 minutes including prep. They did put some lidocaine numbing gel around the area beforehand and that's it. I will admit that the needles did look intimidating, but the actual sensation is totally tolerable. It stings and pinches for a few seconds on each side when they give the injections but it's over before you know it.
Honestly the procedure for me was more embarrassing than anything else. I was bent over on a table while two ladies (my CRS and her assistant) spread the ol' cheeks wide and raised the table so that the "target area" was at eye level

Definitely a wee bit awkward. Mainly I remember trying to think of random things to talk about in an attempt to defuse the social hilarity of the situation hahaha.
The area was a little bit sore afterward, so I did pop a couple of ibuprofen when it was done. But that was really because I had a 60 mile drive through heavy traffic to deal with (in a manual tranny car). I doubt you'll need any painkillers at all, although it might not be a bad idea to keep a few handy just in case the soreness is irritating. You won't be in severe pain or anything.
I don't think the Ativan would hurt, although it might be overkill. Still, if it helps ease your mind about the procedure, taking one would make it go that much smoother, so it's certainly something you can consider.