Wise move. Shakedown runs highly recommended.

Personally, I'd lose the Spam and the cauliflower but everything else looks okay. Three days might not tell you everything, especially if the weather is mild and pleasant, but should give you a good idea of what you can expect long term.

I assume you have a spare tube in there somewhere. You might even consider a folding spare tire; you won't relish pushing a bike with 50 pounds of gear on it.

Good luck and have fun!