On a 50-acre pond, the paddle is almost irrelevant. You certainly won't get exhausted or develop blisters paddling a couple hundred yards. That goes for slow-moving water, too. Fancy, lightweight paddles are for long distances or white water.
I've seen folks adapt folding stadium seats with backrests to kayaks. Any seat with a backrest will be MUCH better than what comes with the 'yak.
Almost any two-bar roof rack will work. You may want to pad the bars with a pool noodle to protect the 'yak. Do use a tie rope from the front of the 'yak to the front bumper of the car - to keep the wind from lifting the kayak's bow.
