"I want Brandon, Teresa and Carly to be there," Catelynn, 18, tells PEOPLE of their proposed guest list. "They'll obviously be there."
In fact, Tyler, 18, foresees his daughter being an integral part of the ceremony. "I would love for Carly to be our flower girl," he says. "That would be so cool – but we'll see."
As for the wedding location, that's another thing the couple has spent time thinking about.
"I would love to go to California [for the wedding]," says Catelynn.
Adds Tyler: "I would love to get married on a mountain or a cliff where you can see the water – something really cool."
Just don't expect to hear wedding bells soon. Though the teens agree they want to get married on their anniversary, July 15, they say a wedding won't happen for at least a few years.
"Oh, it's after college," says Catelynn, while her fiancé confirms, "post-college, definitely. Not for a while."
For much more with Catelynn and Tyler – as well as updates and exclusive photos of the other Teen Mom stars and their babies – pick up this week's new issue of PEOPLE, on newsstands Friday