Valentine's Day brings many unique challenges to parents, depending on how old their kids are. If you have elementary school-aged kids, you've probably had to go to the store and buy way too many Valentine's Day cards for your kid's classmates. It's fun for the kids, but buying and assembling these cards can be a pain. If you've got some moody middle schoolers , you might be dealing with some candy-gram-related drama. Once you age out of classroom Valentine's Day parties, kids start to send eac…