What to do 1 week vacation to hilly area?

Ok, here's my dilema. Currently have two bikes with huasheng 49cc matted to 80 tooth 4G trans. Tops out at around 34 mph. Perfect for my area, but am going to Wildwood mo for a week, beautiful hilly area with a lot of wooded landscape backroads. Without much expense, what would be my best solution to modify the bikes for mostly hilly terrain? Giving up top speed is no problem, as the slower speed to enjoy the scenery is what I'm after.
Thanks in advance for all replies..

The 80 tooth 4G trans is 4 to 1 reduction, I believe 10 tooth output. 48 tooth rear sprocket. That's off the top of my head, hope I'm not wrong.

I wish I could just get the 100 tooth sprocket. But as far as I can tell, the shaft on the 80 tooth will not work, nor the cover. So I would also have to get the shaft, 12t sprocket and cover. I would probably do so if I knew for sure that would be all that was needed. I think the cost we about $69 for each bike.
Although complete 100 tooth trans is $109 each, and swap would be so much easier.
At any rate, I adjusted the valves on the very loose side, brought my torque range down to the lower side of the rpm range. Tried these settings on some hills, helped alot. Hills I couldn't hold rpm and speed before held, and hills that held rpm and speed now it will accelerate up. I didn't add power by adjusting the valves, I just put the power to where I need it the most. Cruising is actually better on flats and slight inclines now, since I don't run wide open alot, having the torque curve in the mid to higher rpm was useless to me. So I will just keep the valve settings on the loose side even after the trip since it fits my riding style.