I'm fine with that.  Adding Marikir's character in after he returns from vacation makes the most sense.  If you want, when Marcus talks to Angus that night, he can discover that there's been a delay in getting David to the island.  Perhaps a bad storm is hitting the town where they where they had sent the alternate members or something.  Or David could be feeling too sick to travel - has the flu or something.  I'm open to ideas.