I love the idea of your son walking you down the aisle - especially since it is your second wedding.
When I got married to my husband, he had two daughters from his previous marriage. They were flower girls, of course, but we wrote in some family vows that he and I said to the girls. We called them up when that part came up in the ceremony. Promises that we'd always be there for them, we'd always take care of them and love them, and that they could always look to us for encouragement and support, love and praise. When we were finished with the family vow part, we lit the unity candle all together since our marriage was also the beginning of our newly created family.
They didn't have to say anything, but the message was clear to them and to the guests that this was more than just a wedding, that by us getting married, they were also a part of that and they felt very included.
Congratulations and enjoy!