I live in Mason -- about a 5 min. drive from KI, but I am more of a Cedar Point junkie myself. (Mainly due to the coasters.) I had not been to KI in several years until we finally went last summer in order to ride Diamondback. Loved it! KI doesn't offer as much in the thrill department, but if you're into coasters, you must check out Diamondback and The Beast. KI is a nice park, and the kids area (formerly Nickelodeon) has always been regarded as one of the best. It has now been converted into Planet Snoopy.
I haven't stayed at Great Wolf; however, I've been there for a banquet, and it's quite nice. I'm not sure how the walking back and forth goes, but GW is literally right next door to KI. I'm sure it's a very short walk. Have fun!
I very strongly suggest that you get to the park as soon as it opens, especially if it's a weekend. Don't take your sweet time getting there in the morning. You will lose valuable "short line" time if you stroll in late. If you've never been, I assume you will want to do a whole lot of stuff. A lot of attractions will have relatively short lines in the morning. I would get there early and take advantage of shorter lines. The summer crowds can be really thick in the afternoon, and even thicker after 5 PM. Check the Kings Island page on this site for a good (ahem) plan to start out the day.
