What's sad is that this culture shames people into questioning whether they ought to depreciate their own precious happy childhood memories, simply because they took place at a now-stigmatized restaurant.

You were a kid then, you had no role in choosing the venue, and you certainly don't bear some kind of moral responsibility for the putative evils of McDonald's as an institution just because you ate a hamburger there when you were six.

Be happy that you got to have fun on a playground with your friends! It is not tainted.