Search the threads for "How to Prepare Your Child For Childcare". It's a one page handout you can give to the mom and dad to help them get ready. Because that's really who needs to prepare, the parents!
Yes, I would integrate slowly if you feel the need. Start with a couple of hours, probably from just after breakfast until he/she is ready for morning nap if he/she still takes one. Then a full morning, with our without lunch, then getting picked up right after nap.... you get the idea.
HOWEVER; I don't allow the parents to come. From day one (after the interview process) I teach that mommy and daddy don't come with you to my house. They drop you off, we play, then you go home with them when they come back. I find it less confusing for the kids. Some of the kids still cry, but those kids will have separation anxiety no matter what. It happens.
Good luck!!