What to cook for my Dad and Stepmum when they visit from U.S.A ?!

Not sure where you are based. If you are in Scotland what about a good old square slice/lorne on a roll? You can never get decent square slice outwith Scotland and can't get it at all outside of the UK. I have to take a whole one with me anytime I visit relatives down south and I missed it like crazy when I was living abroad.
Failing that, what about a simple bacon sannie made with back bacon? You don't really get bacon like that in America. The closest is Canadian bacon, but it still isn't cured the same way as in UK.
Face it, the world over there is nothing to beat a bacon sannie like you had wherever it was that you grew up.
Both simple to do, and so homely.

Life

This is oerfect after a long flight its also quick easy light and very healthy. Roasted tilapia with fire roasted tomatoes and olives. makes four servings you will need 2/3 cup canned fire roasted diced tomatoes 12 small green olives with pimentos cut into quarters 1 tbs plus 1 tsp minced onion 1 tsp crushed or minced garlic 1lb tilipia fillets olive oil spray salt to taste ground pepper to taste preheat oven 400 combine tomatoes w/juice olives onion and garlc mix mist fillets on both side w/oil and season with salt and pepper place in oven baking dish top with mix cook 10-12 mins or till flakey make a side salad of cucumbers onions and tomatoes and otalian dressing one of my favs meals hope this helps

If your family likes Italian food, then have a good sized platter of antipasto, olives and bread at the ready. Quiche and salad are nice, too. Both are fine at room temperature. If you want to cook something, waffles/pancakes are quick-have a fruit salad accompaniment.

Most of all, have fun!

How about something properly british? Scones with jam and cream? Cucumber sandwiches? A bridie with a pint of Tennants to wash it down (OK, maybe a bit early for that)? A Gregg's jam donut?

Honestly, though, I think the best bet is a little platter from which they can pick and choose. How about a ploughman's-style platter with fresh bread, pickles, cheese, roast beef or other luncheon meats, etc. That way they can take what they feel like and leave the rest for another time.

Good old fashioned roast and veg with yorkshire puds, followed by apple pie and custard.

Well is there a dish your dad really likes that he doesn't get to enjoy here in the states?

Have a light snack such as fruuit etc... ready and then prpare a nice lunch.

Nothing beats roast pork with all the trimmings. Very British and filling

just go with a grilled breakfast and toast with fresh orange .and a pot of tea

mac & cheese