You're making me want to make one now.
I would probably have these printed as photos. Trim to size and then I would stick 2 together back to back and laminate with my Xyron. I think they will be nice and durable then. I did this with another project and it feels pretty nice. Could use a fine point sharpie to add more dates. (I just tried with Ultra Fine Sharpie and it didn't write on the Xyron laminate very well). I'd probably round the corners too (I think that would look okay?).
You'll have to show us your finished project!