How important do you think that it is to your children? Are they looking forward to being a part of your wedding? If the answer is yes, it should definitely be a family affair as the bride, groom and the children are getting married. Congratulations!
Second weddings always seem to be more intimate. Start by making a start up guest list to see how many people (family & friends) that you want to invite to this celebration. This will give you an idea of how big or small the wedding should be.