You should take your son to a dermatologist. My son, from a young age, has had a quarter-size cafe ole' mark on his lower back. His pediatrician has always wanted me to be vigilant in watching this. By the time he was 3, he had a about 3 - 4 moles, as you describe. Every year, his pediatrician examines them. This year, his pediatrician asked me to seek the advise of a dermatologist. My son is 11 years old. We have always been conscientious (but not perfect!) about applying sunscreen. He probably has about a dozen of these, now.
Use the A-B-C-D method for determining if the moles are concerning:
A = Asymmetry - are borders evenly round or is there some asymmetry about it?
B = Border - Are border even, border not darker or lighter than the rest of the color; nothing jagged?
C = Color - is color even or are there any lighter or darker colors or spots inside color?
D = Diameter / Size - Check to see if it is larger than the size of an eraser, however, if ANY of the above are factors with the mole, size doesn't matter.
The month of May is National Skin Cancer awareness month. I decided that this was the year my fair-skinned, freckled, family needed to get evaluated. With my love for being in the sun all these years, I got off easy having a few actinic keratosis frozen off, right in the office. I was really shocked that the dermatologist IMMEDIATELY set up an appointment for surgery (actual surgery in a surgical center), for my son, to have three of his moles removed and biopsied. Everything went smoothly, my son was a trooper through the surgery and he is healthy. One mole was really small, however, it was dark, jagged 5mm long/2mm wide, thin line on his forearm. That one didn't even concern me. The other two were that size of a small pencil eraser.
It is good that you are also being vigilant about these moles. I have learned a lot over the last few months. Don't be fearful - just be proactive. This has created an awareness with my husband and children too, about the importance of protecting your skin. We will continue to have regular, yearly check-ups. If you need more information, feel free to personal message me.