DCF wants to talk to my son alone?

DCF was called on us earlier this month, all was lies. I let them talk to my son alone (just him and the case worker). They want to do a follow up to see he is a good weight for his age, up to date on shots and stuff. I know they are going to want to talk to him alone again. I didn't/don't have anything to hide so I let him talk to them the first time alone (also didn't think I had an option). I've been reading up on it now though, is it correct that I can have another adult present while they talk to him? For instance, would my dad (child's grandfather) be ok? Or a neighbor that lives across the street from me? I have an appointment in two days to do the follow up talk, not sure what this means, but I assume they want to talk to my son. I only got the message left on my phone by the caseworker, they set up the appointment at 11am for us with two days notice, we have work and that is the time we go to library storytime. I don't know if they are coming to our house or are wanting us to drive somewhere, I called her back but left a message, she hasn't got back to me. So can I have another adult present while they do that? If I can, and she doesn't want to allow it, is there a document i can print to show her that it is our right?