Realize that DIL now comes first and as said above, don’t criticize her or get son in between you and her. Enjoy and support their love. Make her feel welcome in the family and try not to have too many opinions about the wedding.
On the subject of weddings, I’ve found it’s best to figure out how much money you can and would like to contribute to the wedding, tell them that lump sum and not get bullied by anyone into paying more. If you’re honest about it upfront, they should honor your needs. (That being said, if you give a flat amount, you can’t try to micro-manage the wedding – a bad thing to do in any case.)
And all the things about keeping your mouth shut go even double or triple if grandchildren come.
Remember there is still a place for you in your son’s heart. I am currently having a wonderful weekend with S2, his wife and their 22 month old daughter but I have worked hard to learn MIL 101!