"It just makes sense that I'm having a girl ... I don't know what it is, but I am excited it's a girl," Dane told PEOPLE at Monday night's premiere of Valentine's Day at Hollywood's Grauman's Chinese Theatre.
Asked if they have a name picked out, Gayheart replied: "We have a couple of names, but we're going to wait and meet the baby before we name [her]."
Gayheart's doctor was actually at the premiere, too – which was just a coincidence, though Dane was happy about it. "I think she's ready to go!" he said of his wife.
Dane, 37, and Gayheart, 38, also reminisced about their previous Valentine's Days together, which have been marked mostly by simple pleasures.
"We baked a cake on our first Valentine's Day, remember that?" Dane said.
"We did bake a cake!" Gayheart said.
"It was a chocolate cake with a white frosting on it, right? It was lopsided and kind of messed up, and we ate the whole thing."
Simpler is better when it comes to Valentine's Day presents, too. "She never wanted anything but a card from me," Dane said, "which I thought was kind of weird, because I kind of like to buy stuff ... And she said, 'No, I want a card.' "