No, I don't know who's calling the shots. Some have suggested Ron Klain. Others say it's Obama. I suspect it's a cabal of oligarchs.
IAE, Biden won't be the one deciding what to do about Ukraine.
“Biden’s senility is irrelevant. He isn’t in charge.”
For the most critical aspects of national security he absolutely is in charge and he alone has to call the shots. The military is not going to do nor not do something major on the authority of Valerie Jarrett, Jill Biden, or anyone else.