A follow up from this answer, in which @Doc mentions getting a passport stamp on entry to Canada from the US. I've travelled from the US to Canada and back many times on a US passport, and I've had family members who made the same trip in reverse on a Canadian passort. None of the customs officials (US or Canadian) have ever stamped our passports, undoubtedly because of the close association between the two countries. While having the passport stamped really serves no official purpose, it might be a kind of "souvenir", especially for kids to see when they travelled.
Could I, on presenting my US passport to border control on entering Canada, ask them to stamp it?