I think this is easy to sort and I've done this in the past.
Just cook two curries - one meat for you guys and one mild veggie one for your guests.
Then make something called a tadka - this only takes a few seconds. Heat up some ghee (olive will do if you haven't got ghee) in a frying pan, add a few spices of your choice but plenty of chillies for your friend that likes it hot. In this case I would probably just use sea salt, lemon (not lemon juice, actual bits of lemon), mustard seeds, a few cumin seeds and a sh!t load of chillies). Flash cook it, put it in a small bowl for your guest who likes it hot to add as much as he wants to his own.