Help! Is there a way to allow someone making a booking to add multiple visitors?

I'm at my wit's end here!

Trying to figure out if it's possible for someone booking a free gallery visit that is open only three days a week to be able to include others or will they need to re-book for each individual visitor?

With best wishes and many thanks in advance, Susanne

https://www.ilkestoncontemporaryarts.com/visit