A.C.
Congrats, L.! I am excited for you. I just started biking 2 months ago. I have never done a race or tour, but I DID just sign up for the Ragnar Relay which is a team running race where I will run between 15-20 miles through the Wasatch mountains. Woot!
Since I am just getting into biking, my best advice would be to get a nice gel cushioned seat to help your bum. Push yourself to go a bit further each time. When I first started biking, I would go around the block a couple times, then the next week it was about 1.5 miles to the park and back, now I am biking all the way to the trails and also going to get groceries on my bike and lugging them back in the trailer. I am to about 5 miles each time now.
It is great that you are biking each morning. Maybe push for further distance, or add in a few lunchtime trips to the park for a picnic lunch? Try to go for a longer ride by yourself on the weekends? I also think it is helpful to have a GPS (I use Map My Ride on my Iphone) so I can keep track of my miles and push myself a bit further each day.