Actually I agree with JK666, Niagara (Canadian side) is beautifully romantic and really unforgettable. It should be stunning right now as they put so much work into the gardens and the main street is lined with some of the best flower beds I have ever seen. The podlets might be a bit small for Maid on the Mist is the only problem, which has to be done.
Sheraton on the Falls is a great place to stay - floor to ceiling suite overlooking the falls which are lit up at night, but avoid the restaurant except for breakfast where you have the sun rising and making rainbows over the falls.
The Skylon tower is incredible to eat at with fabulous views.
. And Niagara on the Lake just down the road is such a pretty village. I stayed at the George, which is basic but comfortable and nice and private. It offers a package for a jetpool ride along the river. They do a covered version which would be perfect for the kids and if you are feeling homesick for a pint and a pie there's an Olde Worlde English pub in the town. A fort just outside which would be fun for the boys (all 3 of em) with guns and military dress from the civil war and plenty of space to run around in. It tends to keep pretty early hours - very family oriented. Most restarurants wanted you sat down by 9. And try the ice wine - its exquisite. Vineyards all around to visit and most of the restaurants serve it. The people are really friendly and lots of children about. A good relaxing, clean, safe place to visit with lots to see and memories to make.