Many of us will be celebrating a marriage other than our first one, at some point in our lives. Some of the couples I have married have been together a while. Some recently met. Some come with kids already to be blended into a family unit. Others have kids on the way.
If you are marrying someone with children, or you have them and are marry someone without, or else you both have them, there will be an additional dynamic that you should realize. Blended families take a lot of emotional work and family trust. And they're entirely worth the investment parents and children place into the union. I know this, because I've been both a child of and a parent in a blended family!
Whether your child are young or adult, having them as a part of your ceremony to me is a bonus! I maintain that the folks who come to your wedding have agreed to support the union. This INCLUDES all of the children there. If a child wants no part of the ceremony, it's obvious that there are unresolved issues. I would suggest getting them all ironed out before you take the leap. If a family member isn't completely supportive, I'd suggest that they find something else to do on your day, as the day needs to be about those who have come to join your being joined, not suffer as a martyr in the day.
Can you involve young children in your ceremony? Of course! Let's make sure that they're ok with what they have to do, and discuss some other strategies I have that will cover the unusual event of a toddler meltdown at the beginning of your ceremony. Since I've adopted this strategy, the meltdowns haven't happened in years. It'll be worth having them as part of the ceremony, trust me.
If you have other questions, feel free to ask.