Or do I have to brave the scary shared memory magic?

Unfortunately, yes, at least in your design. Singleton is very uneasy with unadorned fork, since the new process obtains its own copy of environment and memory heap, and can do what it pleases with them without affecting the parent. That is at the heart of Unix process security.

If you want to avoid shared memory, you can define a server which keeps authoritative data.

After Compline,
Zaxo