The key to summer cocktails should be ease of prep. Who wants to spend hours in the kitchen when the party is on the deck? Two ingredient cocktails are best.
Also you want low alk. Highballs and sunshine are a road to an early evening hangover, sunburn etc.
Champagne cocktails meet both of the above criteria. However if you want real flavour, you’ll use real fruit, which will require some prep time prior to the party.
I peel a peach and puree with a couple of icecubes to add liquid. About 2/3 puree and 1/3 Prosecco brings out the peach flavour.
Cherry bellinis are are a little tougher to make because of the handling. Pit and de-stem half a dozen cherries for every drink. Puree with a couple of ice cubes. Same ratio as the Peach Bellini.
Total alk is about 4% per glass (usually 125 mls in a flute) made from 12% Prosecco. Some Prosecco has less kick.