Halflings attacking a planeswalker or battle won't cause Meriadoc Brandybuck's ability to trigger.

Meriadoc Brandybuck's ability has you create just one Food token per player you attack with a Halfling, no matter how many Halflings you attack them with beyond the first.

You can't sacrifice a Food to pay multiple costs. For example, you can't sacrifice a Food token to activate its own ability and also to activate Maraleaf Rider's ability.

Whatever you do, don't eat the delicious cards.

Food is an artifact type. Even though it appears on some creatures, it's never a creature type.