Do I need to adjust time and temperature if I switch from and 8x8 pan to a half sheet for brownies and gingerbread cake?

Your 8-8 pan area is 64 square inches. Half sheet is 9x12, right? Which translates to an area of 108 square inches. I'd 1.5x all the ingredients (If I'm wrong about the measurement, re-calculate the area and adjust accordingly.), and allow for the possibility of increased cooking time because of the larger area. I'd use the same temperature.