My managers group has thirty people in it, including part-timers. Is that a problem?

It is worth trimming. Every order ticket lands in that group with the customer's name, phone number, address and what they ordered, and the riders group gets the dispatch with a link that can mark the order delivered. Treat both as staff-only rooms and keep them to the people who need tonight's orders. When somebody leaves, remove them from the group in WhatsApp on the linked phone the same day. The groups are chosen under Settings → WhatsApp, and every change to them is written to your change log, because they decide where customer details go.