Present is probably the best: "Lancet attempts to turn the undead zombies."
However, you can use past tense, though it seems a bit more difficult in the D&D scenario. Please, no future tense. I find it annoying, lol. "I will run up to the zombie and smash his head in with my mace" <- When, now? or next turn? etc.
As DM I will use some past tense, and present tense (Yes yes, bad Roleplaying style.)
Ponats: First two questions are up to you. (If you read the In Character thread, the Tor is the
only cover from the elements for some miles. So, you will be meeting up there, one way or another (I am not afraid to use a bit of the weather rules

)
Third question: You can describe the area about you (unless we are in a dungeon), describe what your character sees, and attempt to act in character as much as possible. If your character wants to travel with a caravan, then that may be permissible. It will be an interesting twist on the adventure, however the caravan cannot be combat oriented NPCs. So, if you got attacked you would be the one doing the majority of protecting them.
Last question, it appears that you will have to, as the Tor is the only place of shelter.
Also, Ponats. It is definitely possible that during the course of this campaign that Lancet finds her sister. Could you PM me a quick Personality/Bio/Motivation of her sister? That would be great.

And really, if you guys are together or separate etc is up to the players. You can be together, or you can be separate, but the adventure should bring everyone together if they are apart.