I have 2 children of my own, age 1 and 4, and they've been here for every interview. I mostly try to have my little one napping. My 4yo is very helpful and polite, so she's a great advertisement lol. I invite the family in, do introductions, and bring them to my playroom (main floor). I explain our routine, while the kids interact and play. I like to see them in action: do they explore readily? Share? Hit? Throw? What toys draw them in? How do they use them? While observing, I chat with the parents about my handbook (that was already sent to them electronically) and show my credentials (checks, certificates, etc). Then I do a tour, and we go outside to view the garden/yard where children play. It's a nice lead to leaving, yet allows us to chat casually and think of more questions.
I don't do interviews in daycare hours though, as they get a bit crazy with visitors and look bad haha. After the initial interview goes well and I send enrollment forms and contract, I invite them to drop them off during daycare hours, so they can see the children are well cared for.