I was thinking that I have a couple of jelly rolls which would be ideal for this... then I realised that there would be no way of matching the colours for the other blocks!
Sure there is! Find a couple yardages that coordinate, they don't have to be a perfect match. Use those for any places that the jelly roll strips will be too small, and the strips everywhere that they fit. Most blocks have at least some sections that can be cut from a 2.5" strip. If you happen to have a layer cake that matches a jelly roll, then you are all set.
I'm in. And I'm picking up my granddaughter today for some fun, so maybe I'll take her fabric shopping and let her pick the fabrics. A year-long project might be a bit too long for a 3yo to have patience for, but I think if I have a new block done each time I see her, it would be a happy thing to look forward to.