There are a few things you could do to tone down the heat of a hot curry. The first is to halve your curry, put a portion aside and add a couple of chopped potatoes, then leave for half an hour or so. Remove them and reheat. Hopefully they will have absorbed some of the flavour. Another option is to stir plain yoghurt, fresh cream, crème fraîche, or even some coconut cream into theirs just prior to serving time.