Besides the Aquarium, what else is there to do with a 9 year old in that area? Thanks for any ideas!

There are tidepools in Pacific Grove, though watch the surf with caution. There's also a neat kite shop in the American Tin Cannery outlets. Also, a fun Carousel on Cannery row (with an arcade there). Shops and fun places to eat on Cannery Row and the Wharf.

Point Lobos just outside Carmel has easy walking paths from which otters, deer, and hummingbirds can be easily spotted.
Second the tidepools at Asilomar beach in PG.
Depending on the time of year, you can take a whale-watching tour from the wharf. (I think there are still boat outings you can take even when there aren't whales, but I'm not positive.)
Go to the beach in Carmel and watch the dogs play.
You can rent peddle-powered carts to ride along the walking path beside the shore.
You can go check out Elkhorn Slough, a nature preserve about 20 minutes outside Monterey--as I recall, you can take a canoe out.
That's all I can think of at the moment, hope it helps!

If you are taking Hwy 1 out of town, you could stop at the Santa Cruz boardwalk. It's a 45-60 minute drive from Monterey.

NewbE's suggestion of kayaking the Slough is a good one.

I recently took my 14 year old niece for a day.

I've topped the trip report from it. As she did the picking of activities, it may be of help to you.

Thanks to all of you ... Fodorites are the best!

we did Monterey Bay Whale Watch a 6 hour tour and saw dozens of whales, dolphins, and even had some come right up to the boat... I don't know when you are going, so check their web site for seasonal info...