Hi Wylfredo, thanks for posting the relevant rules snippets here already. That makes it much easier.
So, the map basically unlocks the new scenario option for that player whenever they get to choose a scenario. That means, once a player gets to choose a scenario (1-2 or 4+ on the progress table) if that player has the map, they may choose that scenario in addition to the common scenarios.
If you have a gaming group with 4+ players and you are running games in parallel, and if there are 2+ games where players get to choose a scenario and they also have the option to choose the dragon hunt, and both want to play that game, then you will have to roll a die to determine which players gets to play the game first. You couldn't be playing the scenario in parallel games.
I would think about allowing the second group to play the scenario afterwards if the first one fails to retrieve the item. If you are strict though, with the number of games being played and all, I would handle it like this:
1. All parallel games, determines the players and scenarios as usual.
2. If two or more players want to choose a special scenario that can/should not be run in parallel (I'd have to look up which ones this would include), then these players roll dice to determine in which order they get to pick the scenarios.
3. Play the games.
That means, if you lose your die roll and cannot play the scenario since others are playing it already. You may need to wait for another chance to pick the scenario later if the artifact was not retrieved.
What do you think?