We highly recommend this not being someone in the wedding party or close family member. There is a lot going on during the day of, and you want to make sure your family and wedding party are present during the getting ready phase and the picture phase of your day. That designated someone, i.e. handler, should be in charge of making sure the furry one is going potty in the right spot, getting energy out, and making it to the venue.
If you don’t have someone there are companies that you can hire for this purpose, like
Flowers, ask your florist if they are able to make a floral ring for the pup’s collar
Check out Dapper Gents dog collar/bow tie collections! They can even personalize down to the color and fabric.