My daughter was married last year, a truly beautiful wedding. They arranged it all themselves, though I had a million ideas, most of which were rejected!! LOL I learnt to cherish the plans I was included in, and accept the parts where she included the ILs or friends only. Obviously I had a few "I wish..." moments but tried not to be upset by them. I think weddings are such emotional times that it is so easy to become oversensitive. However, I found the nearer to the date we got, the more she needed help and support from both sides of the family - though usually on different parts. And plenty of babysitting was needed too. How about asking your DIL out for a relaxing day to chat all things wedding, a spa day if that is your thing or an afternoon tea. Or maybe host a girl's only lunch, with bridesmaids and her mum. Just a few ideas anyway.
Why not think of something special you could do and ask your DIL if it would help? Be that flowers, or invites, or putting together favours? You may find that would help your relationship as well as being a practical support. If they are off on honeymoon how about looking after the grandchildren during that time. Or having the grandchildren the night before the wedding perhaps? We did both and it was lovely bringing our grandson to the wedding venue that morning to get ready with his mum.
Most of all bite your tongue. I still remember the awful things my MIL said to me during the wedding planning, and that was over 30 years ago. And most of all enjoy!