One thing to consider is your wifes ability to handle the boat in your absence. I have been sailing with my wife and 3 kids (all under the age of 7) for a while when it dawned on me that my wife had never really learned to sail. If I went o/b she would have her hands full. I have been giving her basic lessons over the last few years but this year she decided to enroll in some more intensive classes b/c when we are on the boat she has to devote too much attention to the kids.
I don't intend for this to be a wise crack....
Don't fall off. If it were a 1,000-foot cliff, would you allow yourself to fall off? No. Mid-ocean? No. Wear a harness, to set the example, and don't fall off.
Also, sailing kids MUST learn that their may be times when they need to do EXACTLY as told without question. This voice must be reserved only for safety matters and NEVER wasted on misbehavior, no matter how severe. The two must be separated. At 4 years my daughter would ignore me when I said "clean your room", but if I said "harness and on-deck now" in the middle of a thunderstorm she would do it every time, because she knew it was safety, not something optional.
Much of the cruising I have done was with my daughter and me; no fall back option, but neither would I have a fall back option sailing alone. You have to stay focused and move deliberately.