Does Douglas see the two idiots as closer to nephews than party members?
An interesting idea for this sort of setting would be a need for high-rank parties to have a guarantor of a high-rank noble. Since they're able to fire off such dangerous magic, if the magic went wrong and caused collateral damage, they need someone who can be counted on to pay the compensation. Then the guarantor would have the adventurer party pay it back over time.
Then you could have a plot around the two idiots trying to find someone to guarantee their party without Douglas, but every person they ask refuses. Who would guarantee a party that doesn't want to work with a living legend? The two idiots are caught in a textbook Catch 22.
They try to get out of it by hexing Douglas so he'll retire and become a teacher in a magic academy or something, but his struggles to keep up make the hex way worse than originally intended. Since Douglas drastically strengthened the hex by fighting against it, if it rebounded it would probably kill them. If they survived the hex, they'd be killed by the party's guarantor for their crimes. They just wanted Douglas to retire, but instead they're facing imminent death, one way or another.