I see no need to lower the water level to a few inches. If you need to lower it, it would depend on the size of the tank. A lowered water level would require much more maintenance to keep it clean, and dirty water is not conducive to breeding any species of fish. A few inches of water would also be quite difficult to filter.
The other suggestion I would like to add is to slide a sponge over the filter intake tube so it doesn't suck up any new fry that happen to swim too close to it. When you do water changes on the tank, unplug the filter, slide the sponge off and rinse it good in the dirty tank water, then put it back onto the intake tube. This will prevent it from clogging up and slowing down the flow of the filter.
Your plan sounds good otherwise, just take the temp down slowly... only a degree or so every couple of days. If you drop down too quickly it can shock the fish and cause harm (or death) because they are now used to the warmer water.
Best of Luck to you! Be sure to post some pics here of the fry when the time comes, I would love to see them, and I'm sure everyone else here would love that too.