While on Raro, do the Trek across the Island. We did it without hiring Pa and it tooks us nearly 6 hours; of course we got lost, ended up on the power cable route which required some rapelling and some scary pipe shinnying. Mary still won't let me forget that. Take lots of water.
re Aitutaki: very Cook Islands. I know they've added some resort lodging since we were there. The highest point on the island is about 125 feet ASL. If you're up for it, run the road around the island - I think it's about 12 miles, but take water. I didn't and had to stop and beg. They find runners an interesting phenomonon. I felt like I was carryign the olympic torch - people waiting by the road to wave as I came by. Do the Island night at Ralphies. Lots of eats and music - be prepared to dance