Ew or not, Reinhardt is going to at least give it a hell of a try. So he's just going to pile the plant, his hammer and the dude into the cart before he goes to the front of it. The added weight of the assassin shouldn't be that much more.

"All right" He puts hands on either handle and hefts. He lifts it. There's not much strain. It's maybe slightly heavier than his armor. "I'm going to need you to shout out directions. I've got to concentrate on putting one foot in front of the other. And keep a watch for monsters too. If I put this down, I don't know if I'll be able to pick it back up again." After all, he's old and dragging this all back is going to take it's toll on his muscles.