When i was younger the only reason i got a Happy Meal was for the Toy. Food didn't fill me up. If the was toy banned I'd get a bigger more unhealthy meal that would fill me up!
did you have apple pies and ice cream afterwards? or muffins or any of the other McDonald's Desserts? (or indeed another meal only a couple of hours later?).
the burgers don't have as much sugar in then, nor as much fat as the ice creams likely, so even if kids just get a regular adult sized meal it won't be that bad,
it's not like kids are going to be eating super size portions.
at least they'll be full up and won't require desserts, or another meal only an hour later.