Three days is the minimum for Sarasota to feel like more than a beach stopover. This order front-loads the beach (in case weather turns later) and saves the sunset sail for your last night.
Day 1 — Siesta Key
Get to Siesta Key Beach before 10am; the main lot fills fast in season. Spend the morning in the water — the quartz sand stays cool, so there's no rush to the shade. Lunch in Siesta Key Village, then an afternoon at Turtle Beach if you want to shell without the crowds. Dinner at Siesta Key Oyster Bar if you want noise, or Owen's Fish Camp if you don't.
Day 2 — Downtown & The Ringling
Spend the morning at The Ringling — budget 3-4 hours for the art museum, circus museum, and Cà d'Zan mansion. Walk or drive to St. Armands Circle for lunch and browsing, then Lido Beach in the afternoon since parking is easier than Siesta. Dinner at Columbia Restaurant, a few steps from where you're already standing.
Day 3 — Longboat Key & sunset
A slower day: Marie Selby Botanical Gardens in the morning (shaded, good if you're sunburned from Day 1), then drive up to Longboat Key for the quietest beach stretch of the trip. Close the trip with a sunset sailing cruise on Sarasota Bay — book a few days ahead in season.
Where this itinerary assumes you're staying
This route works best based near Siesta Key or downtown/Lido — Longboat Key is a 20-30 minute drive from Siesta Key Village depending on traffic, which is fine for one afternoon but adds up if it's your home base for the whole trip.