Wood – Vegetable Garden Fence Design with 2×2 Posts

Let's start with the tl;dr: I'm starting a new vegetable garden and need to put up a fence around it. 16'x12', constructed of wood and metal poultry netting. My goals are to ensure that:

1. Squirrels, groundhogs, rabbits, raccoons, and neighbourhood cats stay out. No deer here.
2. The fence will hold up fairly well to small impacts (like a soccer ball kicked by a 5-year-old, or an out-of-control 5-year-old).
3. The fence can be expanded repeatedly in subsequent years, and completely disassembled/removed/reassembled with relative ease (hence no 4×4 posts set in concrete).

Here's how I was thinking of approaching this, I would appreciate your feedback or suggestions:

• Use 2×2's for the vertical posts. I found 42" 2×2 stakes and will drive them a foot deep, so the finished height will be 32" above ground.
• Use 2×2's for rails running along the bottoms and the tops of the posts. Most posts will be spaced 4' apart.
• Use standard 2×4 concealed fence rail brackets to make both installation and removal of the rails easier and cleaner. (Do you suggest something else??). I will line up all the posts, measure, mark, pre-drill, and screw in all the brackets before the posts ever go into the ground.
• Staple mesh fencing to the outside of the posts and along the frame. Extend the mesh a few inches above the top of the fence frame (to deter wood-climbing animals) and bury it a few inches into the ground (to deter some diggers).
• Build a simple door about 3' wide with using 2×2's for the frame (or possibly 1×2's with mesh fencing sandwiched between them).

A couple things I'm also wondering:

• My yard slopes, about 1/2" per foot. Do I slope my fence or do I make sure every post top is level with every other? 1/2" isn't much, my rails should still fit neatly in the rail brackets. Do I offset the brackets on either side of each post? (I prefer the "standardization" since I can move the fence to any other near-level surface in the future, but I might just be acting dumb).
• Should I put some boards around the bottom of the fence for additional structural support, to withstand some extra impacts, etc.? 1x6x8 SPF are $4 apiece (I'm in Canada) = $28 total.

Your suggestions are welcome! Diagrams, images, more info can be provided. I hope this wasn't too long. Thanks in advance!