Wow... Sounds like fun!

I highly recommend you try out some cyclocross bikes. They are basically road bikes that can take fatter tires. They'd be faster than a hybrid but okay on rough pavement or on easy trails. It would be a good compromise. They have drop handlebars, but you might be surprised at how comfortable they are. I was very out of shape when I started biking. I got a hybrid, and never felt so good about the flat bars. After just 4 months I upgraded to a road bike, and have always loved it! You never know until you try...

Good luck!