You can include one or more family members in a variety of ways.
Firstly, keep them involved in the decision so that it is an inclusive action form the start. Ask what each would like to do as each might already have an idea but be shy about coming forward.
Adult members can be one or two Witness.
Others could be Usher, Reading, Maid /Man of Honour, take party in a ring warming or even make an epic introduction of at the end of the Ceremony.
Other options are, a keepsake flower presentation to the couple, with the flowers representative of each parent’s personality, so that both bunches of flowers combine in a vase as one beautiful display but add 1 artificial flower of each type to be kept for anniversaries.
You’ll find a few other ideas here: