I have four children and so far there's no evidence any of them have a tree nut allergy. Two are quite young, so there's still time for such an allergy to manifest itself, but I'm hopeful we've avoided it.
I do have a nephew, however, who is allergic to peanuts. It means when we host a party we have to buy the ice cream that is completely nut free, and when we bake cookies or a cake, all labels must be read! A McDonald's Happy Meal, you'd figure, would be a safe choice.
McDonald's Canada has added a Skor McFlurry to its menu, and that means they can no longer be sure their other products have not "come in contact with peanuts, tree nuts or other allergens".