Best part of the trip is the Dominguez Canyon and Little Dominguez Canyon side hikes...like walking on diamonds... Great pot holes to lay around in and swim. Your cat won't have any problem making it down. I have taken my 14.5 foot Hyside down around this time of the year, and much later in the summer, and never had any concerns. Like Moon says, "the take out at Whitewater sucks", but is worth the trip. Take a lay over day at Dominguez to make the trip well worth it.
"If you boat with your mouth open in the wind and put your tongue against the roof of your mouth, its impossible to pronounce a word that begins with the letter 's'."