He described the idea of popping the question at Christmas as "ridiculous" insisting: "It's a no."
The couple have been dating since April, appearing more loved up than ever when they stepped out publicly in recent months.
Ryan said he is not yet sure if Aoibhinn will be in the audience at tomorrow night's much anticipated Late Late Toy Show.
"These things have to be finalised, I don't know yet," he explained.
His eldest daughter, Ella, will be there to see her dad step into Gay Byrne and Pat Kenny's shoes for the event.
Ryan said that when he landed the Late Late slot, his children were most excited about the prospect of their dad hosting the annual Toy Show.
"The three-year-old isn't really up to speed on it yet and Ella will be floating around in the background. We keep them away from all of that side of things."
The presenter said he's growing nervous as the hours tick down, but says the excitement is helping to combat his anxiety.
Determined to get it right, Ryan has turned to former Late Late hosts Gay Byrne and Pat Kenny for advice on the Toy Show.
"I've spoken to both of them and they were both very generous. They kind of just said roll with it and let it be about the kids.
"Of course I am nervous but that's cancelled out by the excitement. I've always wanted to do this and I've always been a fan of the Toy Show. It's a tradition.
"I've been up to my neck in teddies, toy trains and all the different toys this week. It's a big job, the Toy Show and I can't wait.
"We'll have more kids than ever this Friday, more kids and more toys," he added.
Ryan stepped out last night to officially launch RTE colleague Tony Connelly's new book at a special event at the European Union building on Dawson St.
The European news correspondent's new book, Don't Mention the Wars: A Journey Through European Stereotypes, in available at bookstores now.