If my first post shows up great - it just disappeared mid sentence but I will summerize in case it doesn't. Some parents "shop around" and then from those visits choose a few homes to actually interview with their child rather than drag the child to 15 interviews.

Considering the age of the child and presuming he was in daycare before that there may be things they want to talk to you about that they don't want him to hear. At the same time it is a red flag if they don't want you to meet the child till you have committed. So if you agree to see them alone, make sure they know that you must meet the child before you will agree to anything.