Congrats to all. A happy and stressful time for sure.
Years ago the grooms family paid for all the drinks at the reception but rules have changed so much. Grooms help pick out wedding dresses, many parents are divorced and there are step mom and step dad and half and step siblings.
I would invite her parents and the kids over for dinner and ask what you can do to help. Some families have a lot of money, some don't.
When son 3 got married hubby and I did the pictures for them. When son 2 got married I spent a ton of money at Bed Bath and Beyond.
Maybe your son wants to go on a honeymoon that is extra special and you might want to help pay for that or maybe a down payment on a house.
So many opinions..............So again my advice is to get together with the kids and her parents and see what they need and want and go from there.
And then enjoy this special time. It's gonna be great.