Scenario ideas for one shot - party of dragons

[Melvin the Mediocre]

I'm planning a one shot game for tonight. I'm not going to tell the players what they are, just start the game by telling them they find themselves imprisoned in a tight leather bag. They have no memories of how they got there.

In fact they will begin play as a clutch of black dragon eggs. They are going to be driven by an overpowering hunger, and as they hatch, they will fall upon the other hatchlings and the first combat will be fighting each other for cannibalistic purposes. During the fight, they should easily figure out that they are black dragons in an underwater lair. In this combat, it doesn't matter who lives or dies. Once the brawl is down to one dragon per pc, the fight will stop, the wyrmlings will gorge themselves, and drop off into a torpid hibernation.

During the hibernation, they will connect with a stream of magic and pick their skills and feats. They will then be awakened by a disturbance in their waters. I'm not sure what I want the disturbance to be. It could be the water dropping as kobolds are diverting the head waters into their lair. It could be the approach of a party of skum who have been driven from their old home. After this fight, the dragons should learn that the stream of magic they connected to is reliant on their horde. They will drop off into another hibernation, years will pass, and they will awaken needing to molt. They will have been able to completely pick a new set of skills and feats. They will also know that they most grow their horde to increase the magic and choose better skills and feats as they age.

Over the years, a demihuman settlement will have been built up on the edge of the swamp. The dragons can go and plunder it for wealth and food. The attack will bring the retribution of an adventuring party, which will likely be the final combat for the game.

So what I'm looking for is any advice on what little adventures or combats would be fun to throw in or add to what I have listed above. They all need to be short/easy. This is just going to be a one shot game, and a short one at that.

[Cuup]

Each time they wake up, they will be starving and must feed. Some of their stats are reduced until they're sated.

During one of their hibernations, a Red Dragon of x age categories made himself a nest uncomfortably close to their swamp. They should probably take him out before he decides to expand.

[Melvin the Mediocre]

Oh nice thought on the encroaching red, that seems very draconic.

About how tough should an adventuring party be 3 very young black dragons? I figured 4 elite stat level 5 adventurers with minimal gear, maybe one +1 item each. They will have water breathing spell on them, but I don't know how well they should be able to move in water. Great swim speeds would take away the dragon's big advantage yet having them flounder in the swamp might make them to easy of prey.

[Cuup]

4 level 5 Class-level humanoids equates to CR 7. Making them elite-stat could put them at CR 8, maybe 9. I'd be careful with the balance of that combat. As for the adventurers' ability to move in water: They know the dragons were Black Dragons, would most likely know the environment of Black Dragons, and, being level 5, could most likely afford to outfit themselves appropriately. Therefore, they'd most likely have some form of water walk/breath, as well as Acid Resist. This would effectively reduce the CR of the dragons themselves for the adventurers, unbalancing the combat even further. If I were you, i'd make the adventurers average stats, and give the dragons a full hour's notice of the approaching humanoids.