My DS and I are ofcourse a package deal

We'd love to include him in the vows, as we are becoming a family, the three of us.
There is the unity candle, but I don't want him to handle fire. He'll be 4 and a half when we get married.
I've also heard that many people use the unity sand -- but my Pastor refuses to have that be part of our ceremony. He's a pretty symbolic guy and sees it this way: even though everyone pours their sand in and it combines in a bottle, each person is left with an empty, or half empty bottle. To him, that means that you lose your own individual self.
SO, any other ideas?