Have you considered a hammer and chisel?
It's very likely that you could easily chisel out the extra 1/8 - 1/4" of wood in much less time than it would take to set up a template, much less finding the right bit, adjusting depth, etc.
If you're doing the frames as well as the doors (which would be logical, it's likely both leaves are thicker than the old ones), you'd have to pull the stop trim off the door jamb or make a custom fit template with thicker and thinner portions to accommodate the stop. None of that's necessary with hand tools.
With a nice sharp chisel, you tap straight down all around the edges of the existing mortise to create stops to ensure you don't split out too much wood. You then start chiseling out the "field" from the mortise area, going only as deep as your stop marks. Lather. Rinse. Repeat. Until your edges are as deep as they need to be, then you should (you may have to pause to sharpen the chisel again) be able to lay the chisel flat and hand push it into the open side of the mortise to flatten out the hinge area. The hinge can accommodate some small low spots in the mortise where it rests, you just don't want any high spots, so this isn't rocket surgery, though it may take some practice to be reasonably proficient at it.