Parties for Kids

My brother and his wife are raising my sister’s child, a wonderful kid who is still in elementary school. My sister and her husband passed away, unfortunately, but my brother and his wife have been amazing so far. I’m trying to help where I can. There’s no denying that we’re a little out of our depth, though! Take our current task: planning this great kid’s first big birthday party. We want everything to be perfect for her, but we don’t know much about what makes a kids’ party cool and fun. Should we hire a clown or entertainment, or something? What sets a party for kids apart, and how can we entertain the parents, too?