Windsurfing is great. I have some advice here on on the questions you are probably going to run into.
For the family / beginner board I would recommend something big and wide with plenty of volume, a daggerboard, and a rubber-covered deck. If you want to buy from Starboard, their START and RIO boards are good. Look for at least 80 cm width, and at least 200 liters volume.
For the sails, you will need an extra small and lightweight one for the kids, between 2 and 3 meters squared. You and your wife can probably learn with a sail between 4 and 5 meters squared. Visit a windsurf shop or call a mail-order retailer and see what they recommend.
Of course, more important than either the sail or the board is the LESSON. It is very hard and counterproductive to teach yourself windsurfing, but it's quite easy with a lesson, and definitely worth the money and the trip to get one from a trained instructor.
Also, when you're trying it yourself, find an area with flat water, because even 1-foot waves make it much harder to balance.