We usually all eat together, but it's a bit different as I am working also so we usually both get home at around the same time. Sometimes I will eat first with the boys, if DH is going to be home later. I think it's important for kids to have the concept of eating as a family, and also to learn from watching adults eat etc. So I think you are doing the right thing to eat with them. At some stage your DS might start going to bed later, so you could all eat together then. In the meantime I think it's a great idea for you to have a cuppa or a bit of supper or something and sit with your DH while he eats.