One year I didn't have a job, so I asked at my summer employer if they needed help and lo and behold I became a professional kayak guide for a year and a half.  Our shops were on Monterey Bay and in Elk Horn Slough.  If you have never been, it is worth the trip just to go kayaking for a morning.
We took out lots of kids groups and started doing family tours.  There were all skill levels and languages.  But it didn't matter, as long as you have the right gear and the right mind set you will have a great time!

When getting your toddler ready think about what they need to wear.  Toddlers and Preschoolers don't need a paddle, they need the right clothing and PFD!  If you are in cold water or cold weather get those little ones a wetsuit and cover their feet.  You can use rental suits at our shop but I had to get my own for my little guy...they sizes didn't go that small at the shop.  Use your own wool or fleece socks to keep their toes warm.  You don't need to buy them their very own booties, they will jsut out grow them before they use them again.

Sun screen and hats are a must.  You wear sunglasses so you can see better so get some for your little guy.  If they won't  wear them, the be sure to have a hat with a brim so they can see all the neat stuff and are not blinded by the sun.

PFD when ever they are near water.  Get the PFD that is rated for their weight and skill level.  If you are on the boarder then get the smaller one with the head float on the back.  If they can right themsleves in the regular style PFD then they need the head float!

Get a boat where your toddler can sit just in front of you.  I like the recreational kayaks in Elkhorn Slough, or sit-on-top when you're in the ocean.  Be sure you are comfortable and see if your kid need a PFD for a cushion under the bum.  And your toddler does NOT need a paddle!

If you are not a kayaker yourself then get a guide.  They will show you and your kids so much stuff that you would have missed if you had gone on your own.  Even if you do kayak, I recomend a guide when in Monterey Bay  there is so much sea life you will miss otherwise.

Good paddling!