To cycle or not to cycle on Saturday?

I cycled to the meeting place for a Skyride event that i am going to attend this Saturday. I am not quite sure yet if i want to go through with cycling another 20miles (yes miles not kilometers!). The meeting place is about 2.2miles away, with a few hills along the way, from my flat. The test ride today took me 3ominutes to get there. Good thing about it was that the way to the meeting place, Nuffield Health Centre, have cycle paths/lanes all throughout.

I have until tomorrow to decide. So far as of this writing, only 4 places have been booked. I bet these riders are experienced cyclists!

This may be a bit noob of me. But i am hesitant to change the front gears of my bicycle. I have only been changing gears using the rear gears when cycling up and down the hills. At some point, some hills are really really hard for me to cycle. I have got to muster the courage to change my front gears. How hard could it be?!