Re: Hypothetically if your daycare provider.....
Since you worked in childcare for so long, do you know any pediatric therapists in your area on a personal level? If you do I would just talk to the Mom say you are concerned but you are not an expert. Here is a contact number to someone (please ask therapist's permission first) who has years of study and experience. (S)he can chat for a few minutes and if Mom then feels like there are concerns the therapist can help her set up a free more in depth developmental evaluation through EI. After that I would let the matter drop and not mention it again unless she does. I had to do this with my sister for her foster child. Unfortunately she did not follow through but since the child is in no real danger I have butted out of the process once she was given the contact information. You can only give parents the tools to get help, you can't make them get help.
By the way I call bull crap on you not being qualified to fill out a developmental evaluation as long as you have sufficiently interacted with him for at least a few weeks. The school therapists always had me fill one out on my son all they did was grade it according to an answer key. I do agree it very well might make Mom defensive which is why I suggested the above and then let the matter go since that is all you can do. The only time I advocate getting pushy is if a child is in potential danger due to a developmental or medical problem, then I feel trying to intervene is your ethical obligation as an adult. I am also in agreement with some of the other previous posters. I don't trust a regular pediatricians to do developmental evaluations during a routine office visit. I have never seen a pediatrician do anything close to what a person trained and professionally dedicated to this subject does during a real evaluation.