The movie is an adaptation of the book but follows the book very closely. There are a few minor changes here and there. The most notable difference is Neville Longbottom. In the book Neville plays a much greater role. In the movie, many of the scenes in which Neville played a big role in the book were replaced with Ron Weasley. Ron is greater character in the books than Neville, so I guess the producers didn't feel the movie could hold on its own with more Neville.
My kids loved the book and the movie. Having read all of the books first, I enjoyed the first movie, but there's a lot in the first movie one wouldn't fully understand without having first read the book. I'm not sure it's that great of a movie minus the book, but my kids loved it.
If you and your kids are bored and in a rut, try having family book time. It doesn't have to be Harry Potter, but reading books together is a great way to spend time together as a family and do something different. We've already taken out the second Harry Potter book and sat it on the coffee table. My youngest daughter wanted to start reading it right away, but I needed a day off from reading out loud!