That is a nice find, I would think the two together are more valuable than each on their own. They do belong together.
Trays from Stoyke are sold as a collectables on Etsy and elsewhere:
The whimsical illustrations are by Marcelline Gougler Stoyke, a designer who lived in Evanston, Illinois in the mid '50s. This is one of a series of her designs created for trays. Marcelline worked for Social Supper, Pickard China, Sears, Heisey, Stotter, Federal Glass, and Melmac.