Looking for advice on what the ultimate day trip to St Barts would include.

We have only been there once, 2016 if my memory serves me. It was a spur of the moment decision. We flew out of Grand Case, rented a BMW convertible for around $100, drove around the island lost (phone nav didn't work), ended up at Eden Roc (we could have walked there from the airport), rented 2 chairs and an Umbrella for $120, ate an overpriced meal that was just okay and then flew back to Grand Case. We will be taking our best friends on our next trip and I would like to make it special. Will fly out of Grand Case, but everything else is undecided. Would love to find the perfect bar/restaurant on the perfect beach and see all the "must see" things in St Barts. Your help is greatly appreciated! Thank you in advance!

I love St. Barths, but mainly because I can anchor for free in Anse Colombier.

The walk to/from Anse Colombier beach to the main road is 20-30 minutes along a wonderfully scenic path. This is, by far, the best beach on St. Barths
Second best beach is Anse a Flamands
Shell Beach, just 10 minutes from downtown Gustavia, is always worth a visit.
My favorite, and least expensive, alternative to Haute Cuisine in St. Barths is "Le Select" (a.k.a. Cheeseburger in Paradise) right in the middle of Gustavia.
The roundabout above the airport offers great pictures and views of aircraft landing.

We love St. Barths too! Definitely rent a car get water and snacks, check out Saline, then head to Sante Fe in Lurin for lunch at noon. From there head down to Gouveneur for more beach time. Beautiful and unspoiled, enjoy!

Do any of the beaches mentioned above have chair and umbrella rentals available? Do any of them have bars/restaurants? Thank you!

Anse Colombier - perhaps the nicest beach but nothing there - no chairs, restaurants or other amenities. The beach is considered crowded when there are more than 10 people there!
Anse a Flamands - some restaurants/bars, I don't recall seeing rentals for the beach.
Shell Beach - upscale bar + restaurant. I believe that they have chair rentals as well. Bring the title to your house along as collateral
Gouvernour beach - parking is close by, but no amenities