That's totally fine I understand
And honestly I'm not sure either, I think it really just depends on you and what your comfortable with doing. Most of my shinies have egg moves, good natures, perfect IVs, with my OT and RNG'd by me so I can guarantee legitness. Those factors obviously make my Pokemon worth more than just a shiny but if none of those factors matter to you then you'd probably want more than 1 Pokemon per cake.
So really just let me know what your comfortable with and what you would be happy to trade a cake for Pokemon wise and I'll see what I can do, I'd like to try to get both cakes your offering if possible if no one offers better