The couple, who have been dating for two years, were among the celebrities invited to the launch at Hyde Park in London.
Tom and Dustin explored the attractions, including most of the rides, and seemed to be having a whale of a time as they took selfies before taking off.
The duo wrapped up warm for the festive night out, and it seemed like it was a success, as they couldn't stop smiling throughout.
In October, Tom revealed his engagement to Dustin after an announcement was published in The Times newspaper.
It read: "The engagement is announced between Tom, son of Robert and Debra Daley of Plymouth, and Lance, son of Jeff Bisch of Philadelphia and Anne Bisch of Lake Providence."
Confirming the news, Tom shared a photo of his and Dustin's engagement rings to Instagram to mark the moment, captioning the photo: "#HeSaidYES and then #ISaidYES. Thanks for all the lovely messages!"
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