As a variant on a roast, something like a slow cooked shoulder of lamb or beef brisket can work well. It just sits in the oven indefinitely getting more and more delicious so no timing stress and you can make the sides in advance - with the lamb you can go English roast style, I like potato dauphinoise looks super impressive but quite easy to prepare and just needs to go into the oven for 45 mins- an hour, and roast or steamed veg, or you can put more middle eastern spices on it and go with bulgar wheat/flatbreads, dips and salads (I like the latter as you can include some yoghurt-y dips as a moistener although the lamb does come out nice and soft and tender so doesn't need 'gravy' as such, the gravy is always the most stressful part of the roast for me so I like to avoid 
). The brisket can have more american style sides, coleslaw/buns/chips/salad and BBQ sauce on the side.
Or the other nice thing to do although maybe more summer-y is a mezze spread of different middle-eastern type dishes, hummus, baba ganoush, olives, stuffed peppers, pastries, spicy sausage, flatbreads, couscous, halloumi, interesting salads. This can pretty much all be made in advance and reheated although halloumi is better fresh, and you can also serve 'buffet' style i.e. lots of dishes come out when they're ready/at different times for people to pick at as and when they fancy it rather than having to have it all ready at the same time for a formal dinner! This works really well if you have veggies/vegans to cater for too.
Or for a lower key more informal thing, something like a chilli with all the trimmings (nachos, guacamole, salsa etc) or a big lasagne with garlic bread and salads, or curry (with poppadoms, naans, chutneys) is great, again prep it all in advance then bung on the table for people to serve themselves. The main item can be something you'd have as a family dinner but you can jazz it up with really nice sides to go with it to make it more 'party' friendly...