Forgot to say there are 4 adults and 2 children
You can also go there using public transport, just be aware that a few changes are required in order to get to the rather remotely located town of Gerlos. From Munich Airport you need to go the main train station of Munich using the airport train line in order to catch an express train to Jenbach. From there go on by local train to Mayrhofen and finally by bus to Gerlos.
See whether you can buy your ticket from either German Railways DB (www.bahn.de) or Austrian Railways ÖBB (www.oebb.at/en) throughout Mayrhofen. If not, then only to Jenbach, for the rest buy a ticket at Jenbach Station. For pricing from Jenbach or Mayrhofen to Gerlos see here: www.vvt.at
I personally do not find 356€ for 6 passengers that expensive considering that you get door to door transportation!Edited: 14 December 2015, 19:01
You can make the trip on the 23rd to gerlos buy train to jenbach then the valley train to zell am ziller then bus to gerlos arriving at about 15.37 . but no way can you get to munich airport from gerlos by 10.30 so private transfer sounds the best Hope you work it outEdited: 15 December 2015, 00:21