I use egg crate for my openings too, and never got around to anything more permanent, it works really well! If you don't like the color you can always spray paint it so that it blends in better.
Thank goodness your daughter saw the fish jump. Most of the time it doesn't hurt them at all. I've had a couple of jumpers, including one who landed over 6' away (he upended a piece of driftwood, knocked the heater off the wall of the tank and the egg crate flew off the top - needless to say, we all heard him! lol). That guy scared me the most because of all the banging around that he did, plus the hard landing so far from the tank, but after an hour in the tank he was fine. Lost his slime coat the next day and by the third day was totally normal again. They are tough fish!