make ahead dinner ideas for summer party

Ina's roasted shrimp and orzo is so good! It can be room temperature, so it's perfect. By the way, margaritas has no apostrophe, it's plural. Sorry, I was an English teacher.

I love the idea of a shrimp cobb salad, or even a nicoise salad would be great too if you can get the good jarred tuna in olive oil.
All the components can be prepped ahead and even assemble individual salads or serve with various components arranged by color for a pretty presentation. I would definitely include some salad greens as the base. Most people prefer to make their own plates so you could do a big bowl of the salad greens and then a big platter of the various components, this way anyone can discreetly avoid what they don’t want or like.

I would do toasted garlicky bread with the cobb and just sliced baguette with the nicoise.
For drinks a spiked lemonade, or citrus-y not too sweet white sangria and plenty of ice water and iced tea for those who are not drinking.

If you have a source for fresh smoked fish I have a great recipe that you can increase, Maybe you could have a seafood theme and serve several different salads. https://food52.com/recipes/36456-wilted-arugula-and-smoked-salmon-or-scallop-salad-for-dinner

When reading your question, my mind went to local solutions - both as to type of fish and type of recipe.
FIRST choose local fish and seafood...by lake, river or ocean fishing.
Everything from big mouth bass in the south, to trout in northern cold water rivers, to ocean catch - crab in Maryland, salmon in northwest, etc.
As part of your fish search, consult the seafood watch site of the Monterey Acquarium to learn which species it is currently both recommending for purchase and recommending to avoid (for health of the fish and/or health of the consumer).
http://www.seafoodwatch.org/
SECOND think of regional recipes and things your guests would enjoy.
Soups and stews - if the weather is moderate enough - from chowder to gumbo to cioppino. Always with good bread on the side.
Fish baked in nut crust or salt crust.
Grilled seafood, as Phil as suggested.
Sandwiches, like lobster rolls or fish tacos (what is a taco but a sandwich made with tortilla?)
THIRD once you've caught your fish & your recipe, build the rest of the menu...again, I'm thinking in-season produce and local or traditional accompaniments...rice, pasta or bread.

Without a doubt, my favorite Ina recipe, Roasted Shrimp and Orzo!
An incredible hit ever time I've made it. It's best made the day before and refrigerated overnight. The next day brighten it up with fresh, squeezed lime juice.

How about a Seafood Cobb Salad or a cold salmon and vegetable platter similar to this https://food52.com/recipes/11679-spring-vegetable-and-salmon-nicoise-platter using seasonal vegetables....

60 year olds hahaha high school friends

here's another idea for sides, mozzarella , tomato and grilled veggies

If you have a grill, I would grill calamari and shrimp, You can serve them atop a bed of rice , pasta or nice chopped salad ( greek or regular) grill some vegatables ( zucchini, eggplant , onions) to serve with it. serve with some warm pita or wraps. For sides , a nice watermelon salad with chiffonade spinach and mini mozzarella balls, a cold tortellini salad (oil & vinegar , no mayo) if you don't do pasta as mentioned above. Charcuterie is also nice way to go. I have photo here or you can look at my instagram @phillip.deluca, I have lots there. Let me know if you need more details or ideas. What's the cocktail situation? Good luck and enjoy!

what age are the girls? Do you mean us girls or younger girls?