Visiting Minimerg in October Mid won't be a good idea bro. May to September is the right season. You may find Burzil pass blocked then due to Snowfall.
Regarding booking APV if you hire him till reaching Astore, hire 4x4 for Burzil and back to astore and then hire another vehicle for your way back I think you can save Astore stay expenses of the driver and 2 days rent. But APVs are not very common in GB you will have to hire a prado for return