How about forehead Botox?

I am preparing for my wedding this year, and my mother is worried about the many wrinkles on her forehead, so she is debating whether to get Botox before the wedding.

I'm curious if elderly people also get forehead Botox often. I'm also curious about the price of a single session and what the side effects are!

I am kind of worried that there might be some side effects.

Oh, and about how far before the wedding should I get it to look natural and good, and whether just one session is effective.

I really want the mothers to walk down the aisle confidently at the wedding, haha. If anyone has any experience with this, I would be very grateful for any advice you can give me!!!