Phuket gets hot, so be prepared for a toasty day in the forest. The sanctuary provides water, but heading out for the day with a bottle of your own isn't a bad idea.
The agenda at the sanctuary is very relaxed and is an incredible experience for children. Mine (who were 4 and 1 at the time of our visit) really enjoyed the visit, but did get hot and tired. We trailed off from the group early during the walking portion of the itinerary and relaxed at the tree-top observation area until lunch.
Arrange transportation from your hotel or villa in advance (and be on time!). There is no public access to the sanctuary, so taxis and private cars drop visitors at a central meeting spot — the Monkeypod Cafe in Pa Klok — and the sanctuary's vehicles will take you into the forest.