Yes, your kiddo, with constant guidance and monitoring from you has learnt table manners by now and is likely to eat better and properly when sitting with family at the table. However, he may still need some assistance in how to eat, for instance, he must not rush his food, or not multi-task while eating with family.
What you need to know
When you rush your meal, you are actually not appreciating the fact that food is the fuel that sustains your body. Having a hurried meal in the kitchen or eating in front of the television takes your focus away from the food. If that is what you do regularly, then this is what your kids will also learn. Children learn through observation and if they see their parents giving the least amount of importance to food then that is what they will also start doing.
If you want your child to eat healthy and enjoy the food then start a practice of always sitting down as a family for the meal. A meal is a social experience and the more kids enjoy the experience the more they will love the food they eat. This is also a great way to encourage kids to eat healthy while emphasizing the importance of each food.