Yeah, I think it should be fine. And if you do want to crisp the top of the casserole, you can put it in first, do the higher temperature for maybe 15 minutes or so, and then turn the temp down and put the ham in.
Cool - it all goes into the oven at 11:30 them. I’ll cook the casserole with foil on top & put it under the broiler to brown it when it’s done. That makes sense.