When this question comes up, I often suggest planning vegan meals around starches - potatoes, beans, whole grains, corn, etc. Starches are cheap, they are comforting and familiar, and they are healthy and filling. You can enjoy them as a main course and serve them to the family with a bit of meat on the side. This way, you only need to cook one meal at dinnertime and everyone is happy.
Some examples of starch-based meals: mashed potatoes, grilled corn, salad; split pea soup w/ barley or navy bean soup, whole grain bread; leftover pea soup/navy bean soup over a baked potato [very filling!]; whole grain spaghetti, marinara sauce, green vegetable; bean burritos or enchiladas; haystacks - plain baked tortilla chips topped with refried beans and salsa; three bean chili with corn bread or corn muffins; a veg lasagna, shepherd's pie or hot pot; risotto, brown rice pilaf or savoury rice casserole, vegetable, salad; etc.
You know best what you and your family likes to eat. Make a list of your favourite meals, as well as the meals you cook most often, and go from there. You can probably find vegan versions without too much trouble. Going vegan is so easy these days. We are blessed with many resources.
I hope this was helpful. Good luck and let us know how you make out!