MawB - "“Four Weddings and a Funeral”"
EXACTLY what I thought when I read the OP.
Kiki2 - Please don't sneakily take your dog. If you have specifically been asked not to, then you've been asked not to for a reason. This could lead to an almighty bust-up and could affect your entire future relationship with your son, daughter-in-law, and any future grandchildren.
I do understand how you feel about your dog, really I do. I think unless you are a real dog-lover, then it's hard to appreciate just how much your pet can mean to you.
But it wouldn't be fair on the dog to take him somewhere that it's really not wanted, or welcome. And as has been said by others, where would he be when you are taking part in the ceremony and reception?
I think the idea of finding a dog-sitter is ideal and you have plenty of time to find one, either near to the wedding location, or near to your home, so that your dog and the sitter can become acquainted.