there are different takes on the nature and extent of divine determinism. my theology says god created a system (vs. a sequence of events) and intervenes regularly but not always. part of what god created is natural agency, after all, and in this light "everything that happens is meant to happen" is not synonymous with "everything that happens is distinctly willed by god". my understanding is that god is committed to that agency with such intensity that his position (seeing, knowing, and feeling all) compels him to feel sorrow when he knows both that he can end all suffering and that it wouldn't be fair to. accordingly, he likely doesn't see much value in directly controlling most coin flips
From a cryptographically strong PRNG never reseeded that I would use in every kind of calculation, wharever proximity in any property. That will keep anybody trying to understand things on their toes.
(Note: make sure to give them toes.)
Perhaps those coinflips would not be random from the perspective of an all-knowing all-calculating god, similar to knowing the seed of an RNG algorithm and getting the same value each time when you rerun the program.