I congratulate you on making the decision and actually setting the date. This is an important step.
No I will preface this by saying I'm not an experienced sailor (no bluewater).... but... Our family has a very similar plan. We are a family of 5 with our kids being 8 6 and 4. Our planned departure is Oct - Nov of 2015.
Everyones path will be different, but here is how I approached it. First, I purchased a couple of good books on the fundamentals of sailing (sailing bible, complete sailing guide). Second I purchased an 18 foot pocket cruiser and sailed the crap out of it this season (on a local lake). Third, I follow numerous blogs of families doing this exact thing. Fourth, I spend time on the multiple forums reading the vast amount of knowledge posted. Finally, I will be booking ASA 101, 103, 104 and 114 for early spring of 2015 (I have already been studying 101).
Now the one area of caution is about the forums. Although there are vast amounts of knowledge out there, there is also vast amounts of improper knowledge. Plus some "unique" personalities that can really turn the conversations sour quickly. Some forums are more friendly than others (this one), and some are very sour (CF). You need to take what you read with a grain of salt.