Crikey MIL and the late FIL have/had a strange relationship with food. Both remembered having not enough as children but rather than adopt a "never going there again attitude" scrimped and stinged and all their 3 DC remember being hungry and none remember their favourite dinners. Made worse because MIL wasn't the least bit interested in cooking. What's odd is that they really loved good food when it was put in front of them and were really very greedy. In their retirement they are M&S ready meals.
Anyway, I digress. What do they serve op and do they have rigid issues with food or is this largely your problem?
I'd be heartbroken if family felt like that when visiting us. With MIL and FIL breakfast was free range and she had to sort his because there was ludicrous inflexibility: OJ with bits, Muesli with extra Sun Pat raisins and the top of the milk, a Braeburn apple, wholemeal toast with medium shred marmalade, pot of tea - two bags of chimps. And God help if it was the wrong raisins or not a Braeburn. They also weren't fussy but FIL didn't like/eat: mushrooms, chicken, pasta, garlic, or cruciferous vegetables. I once made his lunch a cheese sandwich with two picked onions on the side - just one slice buttered. I was ticked off for putting the cheese slices in vertically - he liked them horizontal. After that they always had lunch at a cafe as part of their walks.
Usual meals they were served: chilli con, casseroles, fish pie, chops, roasts, baked gammon - all v traditional. MIL had never made a meat pie or pudding.
We rarely eat lunch together as a family. We are usually all busy but the fridge is free range and help yourself: cold meat, cheese, salad, crackers, soup, bread, etc.
Weekend breakfasts, I do tend to make bacon sarnies and variations.
Both DC are grown up. DS has a serious girlfriend who is pescataria. So far I have offered: salmon fillets, pan fried trout, when we have had a barbecue, halloumi, ratatouille (when we have had lamb chops with which it goes), mezze type meals with tsatziki, vine leaves, skewered kebabs, nice salads, halloumi, etc.
I really hope their partners will never fell like you OP. Actually I think the DC would tell me.