Here is an excerpt from the Disney Cruise Line website regarding their Dig tour...
"Wheelchairs need to be standard size and collapsible; no electric wheelchairs permitted. Guests must be able to board and debark the bus or mini-van on their own."
Also this, which implies you might have to collapse the wheelchair in a few places and walk through some narrow spaces:
"This excursion is stroller accessible. However, some portions of the tour may require Guests to fold accompanying strollers."