There are certain aspects of the hostage situation that seem off to me. Typically, these killers would not keep a large number of hostages, especially children, and ensure their well-being while their own lives are at risk. Something doesn't seem right...
so here's my hunch (and I hope I'm right): considering the known self-serving nature of top-brass Hamas, I think they are holding onto the hostages as a last-ditch effort to protect their own selves. They could be keeping the hostages safe (maybe even not in the tunnels) until the last moment, intending to use them as bargaining tools to secure the safety Sinwar, Dieff, and potentially Haniyeh (if he is captured by Mossad in Quater, which might happen soon).