I was watching this episode after the family split up to go on different rides: Greg was with Peter and Mike (at the arcade), Marcia with Jan, Bobby with Cindy, Carol with Alice. If you look closely, Peter is sitting between Carol and Alice on the water log ride, yet in the next shot, Peter is back with Mike and Greg at the arcade. It seems unlikely that Peter would be with Carol and Alice on one ride and suddenly back with Greg and Mike in the arcade.