Not to run things into the ground, but there's something to be said for buying into DVC and paying it off BEFORE having kids. This way, you know that, whatever else might happens, you can always afford a trip to WDW. Meanwhile, you can always use your points at other locations throughout the country and around the world. DVC has agreements with Interval and other time-share companies that allow DVC members to use their points at many of their resorts as well.
Plus, being a DVC members givs you cheaper prices on annual passes, and having annual passes = passholder rates at the resorts. Meaning, you could go to WDW in, say, October, stay at a DVC resort & buy an annual pass. Then, if you want, go one or two more times over the course of that 12-month period, paying for hotel rooms with the Passholder rate (assuming you're not going when blackout rates apply). Then, the following year, use your points to go to California, or Quebec, or Ireland, or anywhere else the points are valid.
Not going for the hard sell, I promise, I'm just saying, there's options.