When I married XDH, our ceremony took place outside the Mass (as he is not Catholic), and it took an hour. Had we had a full Mass, it would have been 1.5 hrs.
Be prepared to sit up front with DD and DS, so they can see what is happening (this is REALLY important, as being able to see helps keep their attention). Have coloring books and picture books.
Sit at the end of the aisle, and be prepared to make an exit, if you need to.
(30) and mama to V