I agree with the others, a boat like an FJ (
) is going to get you wet. If you're careful, it may not happen for a while, but especially as you start to push it, you'll get wet. They are designed as race training boats - that is, they are made to go fast, and that in turn means that they aren't made as much for comfort (including keeping you dry).
Sailing with only the main or the jib for a while, and only in calm or at least not gusty conditions, makes a lot of sense if you want to stay dry. So does not taking your daughter or wife with you the first several times you go out. I would suggest, though, that the first few times you take the boat out, you go out in 5-10 knot winds. Sail around with just the main, and keep one hand on the tiller (the thing you use to steer) and one hand on the main sheet (the rope that hooks to the middle or back of the boom and adjusts how far out the boom is sitting). Learn how the boat feels as she starts to get "tippy" (called heeling). If she heels more than you like, you can hike out (lean back on the high, or windward side) to help compensate, ease the main sheet (my personal preference as it's typically the easiest to do), or steer away from the wind.
Quite frankly, I think you'd be best to gradually sheet in the boom with the intention of capsizing. Learn how far over the boat can go before you'll capsize, and learn how to right the boat (release the main and jib sheets (no sense trying to scoop up half the bay/lake), then put one/both feet on the keel, both hands on the rail, and lean back). You can add flotation to the mast head if you're really worried about it turning turtle on you (flipping upside down). Do that 3 or 4 times that day, until you can start to predict what's happening, and can learn when the boat is overpowered. THEN you can take your wife out with you for a sail or two. If you keep from getting knocked down, then take your daughter out, too.
Of course, NOTHING in the above is a guarantee that you won't all go swimming one of these days. A good gust of wind and a cleated off mainsheet, or an accidental/uncontrolled jibe as you're headed downwind, and you may be in. Any of these can, and will, happen. The trick is to be as prepared as possible, and to make sure that everyone is wearing PFD's at all times.