Welcome, '88. I was your weight (and height) when I started, so you CAN, CAN, CAN ride! Your fitness level could well be higher than mine as I had never much in the way of aerobic exercise. We live in a hilly rural area, so I identified the flattest "around the block" loop I could - it was 3 miles. I had to stop a LOT at first. I was also lurking on TE (I also was doing spin classes at the gym.) Then magic moments came - "here's my stopping place, oh hey, I don't feel like I need to stop" "well, my loop is done, I can go home, wow, I'm gonna try it a second time!" The charity ride is a great goal. Listen to your body and don't overdo, and give yourself LOTS of sweet talk for getting started.

Feel free to PM me anytime. bikes = miracles!