John Travolta would like to expand his family – if his wife, actress Kelly Preston, will allow it, the actor tells PEOPLE.

"There's a thought of this summer maybe trying for a third but that depends on Kelly's schedule," Travolta told PEOPLE at the ShoWest convention in Las Vegas. " I leave it up to her."

Travolta, 53, and Preston, 44, have two children – Jett, 14, and Ella Bleu, 7 – but another child has been on the couple's mind.

"I really like having kids. I enjoy their energy and it keeps everything wonderful and hopeful," says Travolta, who was in town to promote his upcoming summer movie, Hairspray. "I grew up with six kids in my family. I thought I would have five or six."

On watching his children grow up, he said, "It's fascinating always, because they're yours and they're beautiful and they're constantly changing and offering you new thoughts and ideas, so I love watching them grow up...They're your future, really."