I'd say it would have to be very large, considering that wolves in the wild hold territories that encompass miles of land. Depends on how many wolves really. The more wolves, the more territory needed to feed them all. Wolves in Alberta apparently have territories encompassing 357-1779 square km of land, so I doubt any sanctuary could manage that.
Wolves are intelligent animals and bore easily. Novelty objects introduced every few days or so (chew toys, new flavour meats etc.) would keep their minds stimulated.
There is now a growing band of us, who came to the African bush with all our prejudices, with all that 'common knowledge' about hyenas which proved so totally wrong, and who just fell for the spell of animals which were so totally different- Hans Kruuk