The Ontario Science Centre can be a two day trip if you decide to take your time through the exhibits. There is floor after floor of cool things to do and interact with including a special area called Kidspark especially for kids 12 and under.
Exhibits are coming and going and while a few of them look quite weathered they still do the trick and for the most part - kids love it. You can spend the whole day there with kids and you might look at an exhibit and think that it is old and not fun looking, the kids won't care.
It's also a great place for a couple to enjoy themselves. You can spend three to five hours there no problem and hit all the major exhibits.
Movies in the Omnimax are of course educational based but are often narrated by famous Hollywood actors and are rarely longer than an hour long (so you're not stuck in a movie all day).
Food in the OSC is expensive and is currently run by Compass - you may know them from college, university and hospital cafeterias. So bring your own snacks if you want to save some coin.
TO SUM IT UP: Kids will want to return again and again and if you're looking for a weekend afternoon event for you and your special someone this is the place to go.