It's a "do as you see me do" kind of method, ear training. Slowly add in some note reading, but don't rely on sticking to Suzuki for too long, depending on how old your grandchildren are. [/b]
Not to rain on the parade, but I'm afraid my experience with Suzuki has been quite frustrating. I have had at least 10 students transfer to me over the years who have studied piano with the Suzuki method (from several different Suzuki teachers, in two different states). What I've found is that the Suzuki students can mimic exactly what their teacher has taught, but they are not a functional musician. They have no idea how to read music and want everything taught by rote. This disadvantage to the student IMO is great. None of these transfer students were able to create music on their own and musically interpret simple ideas. In short, they can't read music.
All of these transfer students had parents who believed they could play incredibly difficult repertoire. What they didn't realize was that the student learned very few pieces and could not function independently. And isn't that the goal of all teachers, to create students who can function on their own? I know that's my ultimate goal.
I do know several violin teachers whose students are able to switch from Suzuki to traditional without much trouble. I just haven't experienced a Suzuki piano student that could transfer well to traditional teaching.
For what it's worth, that's my experience.