Safety should be your number one priority whenever you are near water. Life jackets should be mandatory regardless of swimming experience, age, or discomfort.
Search for a sailing association or club in your area. Most areas with a body of water have one. Arrange for a class or private instruction for your group from a certified instructor. This is an activity that is best conducted by a professional to make sure safety protocols are followed and they usually provide the boats, life jackets, and are more likely to result in successful sailing.
Be sure to request focus on: safety on the water, basic water rules, hydration on the water, protection from the sun, importance of life jackets, learning the names and parts of the boats, learning a few knots used in boating, and any other water ideas that are important to your group. If your instructor does not provide any details you feel are important, do research and provide it before you go.
Plan for a day outside including: sunblock, hats, change of clothes, water shoes, towels, food/snacks, drinking water.
After the lesson, a general swimming period is always fun if there is a place to get in the water away from the boats.
There are lots of great videos on the Royal Yachting Association YouTube site