Okay, so I'm really happy with how this all went down for a maiden voyage.
First off, the loose, sign up to play structure of the player pool really paid off. I had three cancellations for Saturday's session, but still managed to have a full table, whereas in a normal group that many no-shows probably would mean flagging off for the whole session. What it means under this system is I'll probably have a good shot at a full table next week as the folks who couldn't make it cash in their rain checks.
I'm using a very altered system for 3rd. edition. Instead of choosing skills, the players are offered extra feats, and I composed a list of skill feats that give players packages of three skills at rank 4 apiece. (For example Athletic, which gives you Climb +4, Jump +4, and Swim +4). I've eliminated level limits for skills, and have changed skill progression such that instead of tracking skill points from level to level, instead characters get their level as a bonus to trained feats. This all is very experimental and there could be places where the system breaks as a result, but I did it to ease character creation, giving folks only ONE list to choose from rather than two with very different tracking systems. I also did it to give 1st. level guys a little boost, since the nature of the sandbox is such that EL's aren't bothered with, and the groups could easily get in well over their head.
This manifested in both the druid character's phenominal wilderness lore, and the horseman's amazing skill in the saddle. (We joked that he was capable of bestowing superpowers on any horse he rode.) I was cool with all this, and happy that it gave them chances to really shine even at 1st. level. One of the things I want out of this campaign is for different characters to get a reputation among their fellow adventurers as experts. "Sallum the horseman can work miracles from horseback!" "Serpentus the druid knows the North Woods like the back of his hand." That sort of stuff is grist for the mill, story wise.
I'm also VERY happy that I'm using the "Shields will be Shattered" house rule, which I've seen around the gaming blogs but can't rightly recall who to credit it to. The rule states that you can sacrifice a shield to avert an attack, destroying it in the process. It really saved Sallum from having to drink from the ankheg's acid firehose.
Another thing I'm pleased with is my awesome Customizable Game Screen from Pinnacle Entertainment (available here). I had my hexmap on my side of the screen and found I could mark it with wet erase marker. I tracked the party's progress thru the woods Indiana Jones on a Plane style. Sweet!
Finally, overall I'm really pleased with how the adventure went down. Both engagements of the night were random encounters, and the attack from the ankheg was completely unscripted, but managed to turn into a neat little mission on behalf of the village. The sandbox is working! Hooray!
Anyway, it was a good first session and I'm lookin' forward to next week.
Update: Figured out where the "Shields Will Be Shattered" rule came from. It was concieved by the Trollsmyth . So credit where credit is due. My various players who's character's have been spared everything from giant wolf bites to sprays of acid thank you.