Searching for inspiration.

I recently started re-playing D&D after a break spanning many years and I am due to DM my first (hopefully) campaign this coming Tuesday.

I have the spine of the backstory and first series of encounters planned out here Have also taken liberty of making up 10 or 12 premade level 12 character sheets, although peeps are more than welcome to make up their own as well.

I feel overall I have managed to plan out an opening atmosphere and a series of encounters that should grab the PC’s and keep them hooked. My quandary is what to do for the next session after this one. Do I go ahead and plan it out or do I wait and see where the PC’s go with thiss one and see if any of them make any hints or suggestions with regards to character development and the like? After all its as much their game world as mine?

Any suggestions?