I can offer you this much:
Depending on when I go to class, I can be in a class full of kids, or I can be in a class with teenagers to adults. Usually, at our dojang, the later the class, the less kids.
That being said, I do often go to the class when more kids seem to be there, and on occasion, their parents will be in class with them. And, while it can be awkward at times, I can honestly say that I'm still getting good training. It's all going to depend on your instructor, and how they handle a diverse class. It is entirely possible to go to class with your son and still come home after class barely being able to walk.
So, don't worry about the self conciousness thing. That will diminish in time. If you concentrate on what the insructor is having you do, then you won't have time to worry about kids looking at you.
The other side of that coin is that it really is a better training environment to have other adults in class with you...even if they're a different rank. So if you can find a way to go to a class that you see more of a mixture of adults and kids, that would be a plus. But, it doesn't mean that you still won't get great training...provided you have a great instructor.
