Vegetarians NEVER eat fish what an odd comment
My suggestions:
Casserole one night - you can do a veggie one and cook meat separate for omnis to be added at end or simply serve everyone veggie casserole. Super easy to do and doesn't require you standing over cooking. You could even get pre-prepped veg. Serve with roasties or nice crusty buttered rolls
Chilli - again could either go with making a veggie one that everyone eats or do 2 pots but still relatively easy to do, serve with tacos or tortillas, sour cream, guacamole etc
Burger/pizza/pie and chips night - plenty of veggie versions available to cook at same time as the meat (but you may want to use a separate tray)
Pasta - again very easy to make main part veggie and add meat near the end for omnis - watch the pasta sauces not always as veggie as they may appear
Curry - again everyone have veggie or add meat near end or 2 pots on go at once. If you have a slow cooker you could have the omni in there and the veggie on the hob. Serve with naan, poppadoms, raita etc
Roast - veggies can have nut cutlets or Quorn fillets or veggie Wellington, cook roasties and veg in a veggie friendly way, Paxo stuffing is veggie (cook as stuffing balls - gorgeous hot or cold) Yorkies etc
Build your own salad night - set out family style bowls of salad leaves, cherry tomatoes, slices of cucumber, grated carrot, cold cuts, cheese board, hard boiled eggs... you get the idea. Also accompaniments - beetroot, pickles, coleslaw etc also include some carbs bread sticks, sliced french stick, wraps etc everyone just has what they want.
I think that's 7 ideas