The Ultimate Park Hopper Ticket, as sold at all other WDW resorts, normally must be purchased by ALL members in your party, and must be for the full length of your reservation.
DVC members often have WDW annual passes, but are travelling with family/friends that don't. As such, we are given the option to purchase only as many UPH passes as needed.
However, DVC policy is to only drop one day off the length of stay, either at the beginning or the end, not both. There is sometimes a kind CM behind the counter that will "bend" the rules, but that is an exception I would not count on for myself.
To work around this, you may have to split your reservation into two separate reservations. This would allow the you to drop the days you don't want without having to argue with a CM simply doing their job.
Prices for UPH (and other media) can be found right here on the Dis @:
WDW Theme Park Ticket Prices
The DIS has 3 night/4 day UPH listed as
$231.08 Adult Gate
$185.50 Child Gate
$221.54 Adult Advance
$177.02 Child Advance
Hope this helps, Steve
