Resorting to a gag gift for an anniversary present is a very sad reminder to both you and W that (1) your M is not what it should be, (2) your W doesn't believe it can be what it should be. If you are in a position in which it is not appropriate to get a gift befitting the occassion, then do not get a gift. In such cases, all a gift does is highlight the problem.
If you cannot stop yourself from doing something, perhaps just tell W DIRECTLY what is going on and make a DIRECT invitation, "Celebrating our anniversary right now doesn't feel appropriate right now, but ignoring the day is odd also. How about we just celebrate our family, and I take us all out for some nice chow?"
