If dinosaurs had penises, they’d be similar to a ducks. They had cloaca, and duck “penises” are basically something that fills with fluid (not blood like in mammals) and pops out of the cloaca.

There’s basically an evolutionary arms race between duck penises and female duck cloacas - they have false paths so that they can redirect sperm that isn’t wanted. It’s not that hard to use that to speculate about dinosaurs…