Thanks for your solutions! I was able to get the first one to work, using the page ID, but not the second one, using the slug. And unfortunately I do need to use the slug because sometimes I'm dealing with slightly different instances of the database depending on the environment and so the page IDs aren't always the same. Any idea why using the slug didn't work?

Thank you both. I will take your suggestions/comments into consideration. Regarding using a taxonomy rather than meta keys, I had a similar thought, but was trying to keep my taxonomies clean, but this might be my only option.