Boy, if the witches isn't a fun place to bring a toddler I don't know what is!
Used to scare me on the Doris and Sophie, never mind a smaller and non-metal hulled boat.
You should be able to find a few fun things for your toddler to do right at the Weirs, but most of that stuff is geared towards older kids. A train ride complete with ice cream sundays are a good bet, as are some of the arcades. For dinner you're right near our dearly beloved Waldo - Peppers and Willows (more formal), and if you like Mexican the Crazy Gringo is a very good bet.
Good luck and enjoy.