I had a spare 50W panel and charge controller that I used similarly for camping. Had more or less the same thought as you: I should use this year round.
Ended up building a wooden box with a couple of old car batteries inside along with the controller. Kept it outside and ran a cable inside carrying 12v (make sure you put an inline fuse after the battery in case it short circuits along the way). Used the 12v from that and some old car chargers to set up a charging station for all my devices.
The car chargers were all random plug styles since they were from a box of stuff I've accumulated over the years, so I cut those off and spliced on USB-A female ports so they could charge any USB device. I eventually ran a second pair of 12v wires so I could run a small 100w inverter from the batteries.
Worked great, but the car batteries crapped out after about 3 years (in all fairness, they were junk to start with).
If I had to do it over again, I'd do it similarly but use 12v USB-C power-delivery adapters instead so I could charge bigger stuff like my laptop without having to use an inverter.