Which dog should accompany us?

Saturday there's a fall festival in my hometown. Everyone(including leashed pets) are welcome! We have a 14 week old shepherd mix puppy and a year old black lab great dane mix. It's already gonna be my husband, my year and a half old son, and myself. My husband will be pulling the wagon so I can hold only 1 leash (can't do a coupler cuz my labx would drag my shepherdx) I'm thinking we'd be walking too much for my puppy but I'd feel like he felt left out being left at home.. BUT the puppy gets to go places more often than my big dog. What should I do? I really want at least one of them to go. I don't think Armando(puppy) would ride in the wagon, he'd probably jump out and get hurt. But I don't think Duff should stay at home again because he LOVES people and dogs.