DADDY GLOVES: An outside the box
When you select the 2X material for the project, pick the widest boards you can find. The boards generally come from closer to the center of the mill log. Then, if you rip the project stock off the outside edges you will wind up with quarter sawn or rift sawn stock to glue up. The pith material left from the ripping can be used in less visible project parts. If you use splines or biscuits to align one surface you will seriously degrade the dimensional change. As TMS points out, elongated attachment holes in the battens under the top will allow for whatever movement there is. The point about breadboard ends is well made also. One down side of ripping the stock is that you give up any cathedral plain sawn grain look the boards have as planks. Just another cat skin in the hopper with hopes it will be thought about