Make two reservations and cancel the one you don't use. 2015 Mustang is unlikely, as I doubt those will be going to fleet sales very quickly. Current-generation (2014) Mustang is a distinct possibility. 2015 Tahoe I would say is extremely likely (or its sibling the GMC Yukon).
No Toyotas or Chryslers fall within the "Luxury" class so no worries for you there.