What are the eating preferences of the people, e.g. are they traditional 'British'/plain familiar food type lovers or would they enjoy something more spicy or adventurous? Is this for a dinner party or special occasion or more of a homely simple meal?
My simple/easy favourites to cook for a crowd are a veggie curry (spinach, chickpea and tomato my current favourite) which you can either serve very simply with rice or more fancily with all the indian trimmings, naan, poppadoms, pickles, raita etc. Or a three bean chill, again either simple rice or you can do as a serve your own taco/burrito station with lots of different fillings, cheese, sour cream, salsa, guacamole etc. Or a veggie tagine with 'jewelled' couscous and perhaps some middle eastern sides. All of these can be prepared in advance and reheated on the day and you can adjust the spice levels to suit the tastes of your guests.
However if my guests were not fans of any spice/'exotic' at all, I might go for something more like a lentil shepherd's pie or veggie lasagna. And if I was trying to really impress I'd do a mezze feast with lots of different dishes, hummus, muhammara, baba ganoush, olives, flatbreads, bulgar wheat salad, spinach and feta pastries, halloumi, tomato salad, fattoush salad, stuffed peppers and aubergines, perhaps a persian 'kooku' frittata. All of that can be prepared in advance except the halloumi but looks super impressive as there's so many different dishes to fill the table - can be hard to eat if you are going for a sit down though so it lends itself to more informal serving.
Happy to share any recipes if helpful?