if it was me, beside putting lights on the kayak i would also attach a whistle to my life vest and bring a small waterproof flashlight as well maybe waterproof matches if i can find room on my vest to attach them. If the kayak tipped and got away from me at least i would have some safety stuff with me to grab someones attention and maybe make a fire if i had to. Ok i know maybe a little over board but i have heard of people getting hypethemia in august from being in the water to long.
Cheers!