It would be possible to "do" all three in one day (provided you have the right keys/permits etc in place),
Start off in Stainsburys, (get a bit muddy), pop into Grebe and help Cap 'n Chris with digging, then wash off in Waterwheel!
After that retire to the "Center of The Universe" for liquid refreshment, before retireing to your chose caving hut for a nightcap and bed, followed by more underground shennigans the following day!!
Better to regret something you have done - than to regret something you have not done.