There is a spot on the web says they will customize a tour for a group -. Aleyska Resort could be a nice getaway, but, we really want to do Denali and we'd probably pass on the resort. Biggest reasons we are doing Alaska again is to hang out will all of you and to see Denali.
I found a spot on this site - we need a minimum of 20 for a group tour. We have over 60 on Mush

Editing to add, I asked them for info for a group of 20-35 upscale accomodations inlcuding transportation from Whittier to Denali to Anchorage. Info is free.

http://www.premieralaskatours.com/docdisplay.cfm?docID=19 Tour sample