I would choose the second option. Not only do I think that's RAW (no interleaving of actions on your turn), but also that I expect a closed door to cost a little more time than an open one. Having to spend a minor action in the middle of your move is an almost negligible cost - it might as well have been a curtain in that doorway.How is this done, where do move and minor actions start and end.
Can you move 3 to a door, minor action open, then finish the move to go another 3 squares ??
Or is it move 3 to door (end of move), minor to open, another move action.
Yep that sounds fair.
What about free actions, such as Wardens Mark, can they be inserted part way through an action:
1. Part way through a move - I wouldnt think so.
2. In a charge, at the end of the move part, but before the attack ?

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.