Honestly, don't stress over it. At six months, if he doesn't want to eat something, then don't give it to him. Try again a different time. I don't even feed my kids solids until they are older - closer to 8 months with my current baby. With my other three, they were closer to 10-11 months. And, my first two were still mainly breastfed until 14 months because they had very little interest in food. They are all well sized (not overweight), healthy little people. And, it's been surprisingly common that some kids aren't very interested in food until around that age.
I only share all that detail to reassure you that making sure your baby eats veggies at six months is going to have very little to do with his health later on. You want him to enjoy eating veggies, and if it turns into any sort of power struggle, he's going to hate veggies more.
Right now, just let him lead with what he likes and doesn't like, and don't worry if he won't eat certain food groups. It really, really is okay. He'll develop those tastes later on. My kids love fruits and veggies. LOVE THEM. It probably helps that I don't give them any snacks other than fruits or veggies so they aren't used to sugary foods:-)
Anyway, really, really, really don't worry about it - it doesn't need to be a big deal at all. Six months old they don't even need to be eating solids. They CAN eat solids, but it's not necessary for their nutrition. Make healthy eating fun and not forced.
The biggest thing is if you are healthy, your son will learn that from you. It won't matter if you have obesity elsewhere because you are the one feeding him and teaching him what is good to eat or not. I have obesity in my family as well. Some of my sisters are overweight, and i'm seeing that their children, as they get into their later teens, are gaining weight too. I don't see that happening with mine (or yours) because we do things so much different at our house!