Best way to distribute bitcoin to heirs in a will
To meet your requirement of freely using your bitcoins and moving them around, a deterministic wallet such as Electrum may suit well. In that case, you'd just need to share the wallet seed (and some details on how to use it), perhaps with half of the seed stored in each of 2 secure facilities to protect against theft.

That doesn't meet some of the other requirements, such as handling an equal split, but writing a will could handle that part reasonably effectively (though still with some chance of human error or fraud).