Another thing to keep in mind is that speed is your friend. Get up and get down. The more time you are on the upper part of the mountain, the more chances you have for bad things to happen. My advise, given your situation, would be to forgo the sleep over at Helen Lake and do it as a day climb. Sleep at the parking lot or maybe horse camp on Friday night and get up early and start walking. Helen Lake is a little Woodstock-like this time of year and not in a good way. Carry plenty of water and your warm clothes and little else.
Shasta was the first hike/climb I did above 10,000 ft and I was a novice at the time. I seem to remember waiting for my partners in the parking lot at 2:30 or so on the way down and I was older and probably less fit than you. Enjoy the conga line and be open to turning back if things get shitty. Good luck