Other mistake: It makes no sense that the tartan that Collin's mother puts on the wedding dress does not match the tartan that Colin is wearing at the Highland Games. Clan tartans are a big deal in Scotland so this makes no sense.
Other mistake: In the scene of the wedding rehearsal dinner, when everyone is toasting, there are people outside the restaurant's door just standing there looking at how the scene is being shot.
Other mistake: In the end credits, the pseudo-newspaper text surrounding James Marsden reads "The best man was Kevin Doyle's long-time friend and colleague, Trent, who has [James Marsden] The best man was Kevin Doyle's long-time friend and colleague, Trent, who has recently taken over." The part before the actor's name is repeated immediately after.