My biggest problem in moving around the garden is uneven ground. My dream is to put smooth walkways all around my property. I am not in a wheelchair now, but have been and may be again in the future. I have a nice cart my father in law designed and had a welder make for me from stuff he found in a junk yard. The base is from a push lawnmower, with small front wheels that pivot, and large bicycle wheels in the back. The thing acts like a walker for me and has room for two garbage cans, or several sacks of mulch, or plants, and a bucket with my tools. It even has a seat for if I get tired far from the house. It's big advantage is that it doesn't have to be balanced like a wheelbarrow. I would not be able to manage that.

For people confined to a wheelchair, a cart like this could work, since it carries everything heavy. I don't know how you would push your chair and the cart though. Unless you're motorized. -- Marie

I like the green thumb brand of reinforced fiberglass handles, they are about 2/3 the weight. I also use aluminum pizza peels (spatulas or spades) with 2 ft and 4 ft handles when I am working loose soil. They are pricy but I think the 4 ft long one weighs about 2 1/2 lbs. I also like a 2 handed grill scraper for a hoe. They have a replaceable steel blade and an alum. body. I even use it for splitting kindling.
I also had a cart something like Marie's. It was powered by 2 motorcycle starter motors that powered 2 rubber tracks and steered with a joy stick. It could move around 300 lbs and pull me at a steady walking speed. My brother-in-law built it for me. He had a but it was set up as a stair-climbing hand dolly. I saw it carry a 20 cu ft freezer up 4 flights of stairs and not miss a lick. All he had to do was balance it.
Marie,
I have used crushed cinder block for paving walks. It is great, cheap, easy to use, and it won't hold water. I just spread it between 2 2x6 retainers and then had it packed with a heavy roller. It would even take a w/c without bogging down.