Neutered male dog loves to hump

I have a five year old male dog we rescued as a puppy from Texas. Shortly after his adoption, we enrolled him in puppy school. He did well and enjoyed other dogs. He’s smart, very sweet and a total mama’s boy. Over the course of his life, he’s displayed some fear aggression. We’ve learned how to deal with it and to read his cues before he gets to the aggressive stage. He likes to show our other dog he’s the dominant one, despite her being much bigger than he is. They get along 90% of the time, but sometimes they get into it. He loves people — sometimes a little too much. He gets excited and starts to hump. He humps men, women and worst of all, kids. We have a three year old — he’s very good with her, but we are sure to never put them in dangerous situations. Whenever we have friends over, we have to put the dogs away because he has knocked kids over while humping them. I’ve had dogs my whole life and never had to deal with this before. It’s not something he does constantly. I’ve noticed it’s increased as we come into spring. The past few weeks he’s been doing it a lot more. What can we do to stop this behavior?