I say, go for the seasoned captain, whose last ship was destroyed, killing his best friend, and he feels he needs to atone for that. He's a little angsty, cautious, and aloof, compared to a dynamic first officer, who has risen through the ranks quickly and wants to prove himself ready for command (more to himself than others).
I would use Riker to help flesh-out Picard and make him more interesting. Picard would see in Riker himself at that age and clash with him over issues related to playing it safe. Riker, while respectful, worries that his Captain may be overcompensating.
The reckless rookie paired with a seasoned and somewhat cautious veteran has been done before and could work here. This way, it wouldn't require you to change much about Picard and it would give you a character arc, where he goes from angsty, cautious, and aloof to facing his past, overcoming his angst over Jack's death, while being willing to take some chances and open up to his new crew.
In other words, focus more on what Picard became than how he started out. Then in the first movie, have him make that journey in a quicker span of time, leading to a re-energized, more confident Picard for the sequel.