At 5 they'll be a bit shy/ stand-offish at the beginning so start with a good warm-up game eg musical statues and give them a sweet when they are knocked out. I'd have quite a few games (say so mins worth: musical bumps, musical staues, pass the parcel, the mummy game 9in teams they have to wrap one person in cheap toilet paper to look like a Mummy), pin-the-tail-on-the-donkey/ witch on the wand/tiara on the princess, team balloon bursting. Have the room set out with some toys around (dolls house, dressing up clothes etc) so they can play a bit themselves.
Then do food after 45 mins or so:put a table cloth on the floor and they all sit at it and you serve drinks, cocktail sausages, popcorn. Then serve rice crispie buns/ fairy cakes etc.
After food either let them loose in the garden or have a longer game: in the past we've got all the kids bring a teddy and then they choose from all our dolls clothes and dress up the teddies and we do fashion show. And use some of the many bead sets you've been given in th epast and get them to make necklaces for the bears. In our case it helps that we have 3 DDs so lots of dolls clothes (&a few newborn babygros) & more bead sets than I know whatto do with
The most important thing, ime, is that they actually love just playing themselves so if you have a decent garden and reasonable toys, you don't need to account for all the time they are with you: certainly last 30 mins they can just play.
Oh, you can't beat balloons and bubbles for simple fun!