Sounds like you're making good progress, Redstone5. Well done.
To keep it going long-term, though, it sounds like you need (if you haven't already) to get your husband on board. I can understand a teen not wanting to carry soup to school, but your hubby's feelings (boosterism?) for store-bought cereal is just silly, both financially and nutritionally. You're making great strides already, but you can't keep the pace alone. Everybody's got to be on board with you.
Everyone has already given great advice. One thing I'd suggest is maybe doing make-ahead egg dishes for breakfast to rotate with the homemade granola/yogurt option. Similar to the quiche and egg bake ideas, mini frittatas (i.e., scrambled egg muffins) are easy to whip up with whatever veg/meat/cheese the family likes (doesn't even have to be identical since you can add different ingredients to each one), and can be kept in fridge a few days or frozen. Microwave and add a pat of butter or olive oil, and you've got another inexpensive, low carb, high-fat meal that won't leave folks starving in an hour AND is easy and fast for husband or the kids themselves to prepare in the morning.
I, too, hear ya on the lower-carb eating. I do so as well, and while the individual LCHF ingredients can be more expensive than grains and starches, our grocery bills overall haven't risen so much simply because we don't end up eating second- and third-breakfast, plus tons of snacks and dessert.