I don't expect to be doing the F&W passport because I don't expect to be doing more than one or two booths, but I have done similar things with kids. The randomness is what gives it the charm and sense of authenticity. On our last trip to Canada, our passports were stamped on a random page in the visa section, which surprised us, since on the previous trip they weren't stamped at all. But we need to flip through all the pages just to find the stamp, and that, too, is part of the authenticity. They're not supposed to be neat and organized.
I'm sure kids can have fun with the stickers, and obviously some adults prefer them, but to me, the stickers would make the passport lose all value.
