Everyone's suggestions are great. Perhaps also a few readymade salads from Waitrose or M&S, served in nice bowls, which will be a good starter and also an alternative for people who find lamb or pork a bit heavy. Salads with chick peas, chicken, etc. are filling and tasty and can be a meal in themselves for lighter eaters.
I usually do a cheese board after, in case anyone didn't get enough or didn't like the food.
The main thing is to be relaxed, and not rushing about, as your guests will feel uncomfortable if you seem harassed. Just laugh off any disasters. Focus on how grateful you are to have such nice friends, who are happy to give you their time and their company.