To think this is an insurmountable menu challenge?

[heelhunk]

I thought I could cope with a family gathering with a range of dietary requirements, but I've just had two last-minute vegans added into the mix.
So now I've got to provide lunch and tea for 13, including two coeliacs, one also dairy-free, one diabetic, one wholly carb-free, one high protein, one vegetarian, the two surprise vegans and a teenager who seems only to eat cucumber and cheese free pizza. The remaining guest are big eaters, who love their puddings.

Shall I emigrate, or develop strategic Covid?

Yes, Lidl sell vegan snacky bits, usually the GOSH range of falafel type things which are also gluten free. They usually have vegan cheese, ice cream and sometimes fake meat slices. Sometimes they'll have pots of puddings too. They might also have frozen sausage rolls, but the freezer range changes often. You can get ready made vegan meringue but not many places will have it so you might not want to bother looking. If you can still get it, glitter jelly sachets are vegan (check each colour in case its changed), Hartley little pots are mainly vegan too.

Big pot of vegan coconut milk based veg curry. Big dish of rice (or a veg biriani). Some meat skewers plus any easy extras you fancy (samosas / meat and/or vegan sausage rolls / mushrooms bruscetta). A couple of shop bought puds.

Your family take the mick. Many people do these days with 'likes' dressed up as 'requirements'.

You're not a chef at a restaurant.

Unless it's an allergy, it's just a preference so I would make something that suited ones where there is a medical requirement and ignore all the others.

Courgette and coriander soup - vegan, low carb, no gluten

Vegi stock cube - check it gluten free if you can't get on then some fine mixed herbs work.

1/2 to 1 courgette per person
boiling water
oil

slice the courgettes then swat in the oil in a large pan, once they are translucent add boiling water and stock cube - simmer for 15 mins - this can be served hot or cold, in this weather I'd go for chilled.

As an alternative hummus with various things to dip, cucumber for the child, pepper slices, bread sticks and chees straws kept away from the celiac.

Korean lettuce boats. Basically a little gem lettuce leaf with a protein and a sauce - ask the celiac to tell you if any shop bought sauces are OK, if not then lemon juice and fresh mint can work.

Shop bought sweet chili, soy sauce, even apple sauce

The protein can be meat or tofu, stir fried or oven baked, you could even do fish if it's 'meaty' eg sword fish. Some people add sesame seeds (does anyone have an allergy?)

On the side serve salad, a slaw made with grated carrots and finely chopped spring onion with a little lime juice. Offer rice to those that can have it.

Pudding - er fruit salad? Maybe with some meringue and offer cream / yoghurt / Yofu

Good luck?

For those suggesting lentils and chickpeas they are very high in carbs. When I low carb I don't count them because they are such superfoods, but the majority of low carbers won't eat them.

Low carbers and high protein is more usually balanced over the course of a day not a single meal. I would interpret this as a preference rather than a dietary requirement.