Thanks for the advice (and another interesting link from Kaukau). I think my buddy, as a first option, is going to see what rental places are near the hotel to see if he can do the daily rental thing or work something out with them.
I was visited Honolulu three and four years ago and remembered parking around Waikiki to be pretty difficult. The first time, we rented a condo nearby so we didn't have any problems. But the second time we stayed at a rental on the north shore and when we visited Waikiki, I think we ended up parking along Ala Wai once and did some pay parking in a grocery store parking lot. That's too bad about the loss of a lot of the Ala Wai parking (if just for a short term).