Check and see if a local shop has a freebie how to change a tube class. Grab a spare tube and a set of Pedros spoons and throw them in the bottom of your backpack. The only failure I have had out has been tubes. Not a bad idea at all to pick up a bicycle multi tool or a metric folding Allen key set in case anything comes loose. I'm still just using a backpack. I put a rack on my commuter and didn't not find any use for it without panniers myself. I would pick up a taillight for the times you will be on the street. Planet bikes blinky3 is about 10 to 12 bucks and is a great little budget taillight.
If the sidewalk is empty, go for it. There is absolutely no shame is lowering your own level of risk. Heck, I have a 5.5 mile journey each way, and half of it is by sidewalk due to the roads I would be on and the fact that they are usually abandoned.
Have fun. It's a great way to start and end work days, and that much less carbon emitted into the atmosphere that your kids generation will have to figure out how or if it can be fixed.