My suggestions:
Farm only plump helmets. Make many small farms instead of a few large one for greater redundancy against tantrum-induced damage. Have a large food stockpile that takes only plump helmets, and a smaller stockpile that only takes plump helmet spawn.
It will require some micromanagement to make sure that there are always a few dwarves with the planting labor enabled. You don't want to enable it on everyone because yields will suffer due to poor planter skill, but you need to make sure that you still have enough farmers to keep the fields planted.
Embark somewhere with a steady, safe water source, and build a few dozen wells.
Embark with a lot of wood, make a lot of beds, and build them all in a single large common barracks.
To keep your dwarves happy while eating plump helmet and drinking water, give them a very nice dining room, and if possible a waterfall under a meeting area. (Note: this may cause an unacceptable drop in FPS, so it's best to try and keep happiness up in other ways is possible)
Do not kill immigrants. You're going to have a hard enough time keeping up with putting everyone in coffins as it is. Instead, build a safe immigrant airlock using bridges to let immigrants in while keeping ambushes and sieges out.
Traders will be a problem. If you don't trade with them, they are likely to die, and then their ghosts will haunt your fortress. The safest way to do this will be to wall off the entire edge of the map with raising bridges. If you do that properly, nothing will spawn - no immigrants, traders, diplomats, wild animals, ambushes, or anything. You'll need to take them down periodically to get fresh blood for breeding in, I expect, and that's going to be a problem as your own hoards of idle dwarves will produce enough children to push the population over the cap.
Of course, you need to get a breeding pair of dragons in the first place for this to work. I did some research a while back when trying to set up a Roc farm. It is possible by cleverly poking through the files you can export in Legends mode to determine how many of each megabeast there is in the world and where in the world their lairs are. I don't know if embarking very close to a megabeast's lair makes it more likely that megabeast will visit you, but if it does you could try finding lairs of male and female dragons and placing your fortress as close as possible. Of course, if you're running a pocket world, your fortress will be close to them no matter what due to the tiny size of the world. You may actually have to go through a lot of pocket worlds before you even find one that has two opposite-gender dragons in it.