The Happy Scientist, we demonstrated all three with a scale and some hand weights.
I created a worksheet so they could fill in all the different demonstrations we did during class. I did a demonstration and then read from the book, did another demonstration, and so forth.
The First Law is that of inertia. I placed a baseball card on top of a glass, and then stacked coins on top of the card. I asked them to predict what would happen to the coins when I horizontally flicked the card away (they said the coins would fly off everywhere.) Of course they dropped into the glass, and I let them try it a few times. I also gave each of them some thick paper (bookmarks, actually) and a stack of pennies. I instructed them to place the bookmark on the edge of the table so half of it was off of it and then to put a stack of coins on the bookmark. They quickly pulled the bookmark out from under the coins and the stack remained intact on the table. (The boys, of course, experimented with ways to make the coins spill...)
Another demonstration we did used a wheeled cart and a stuffed animal. Shoving the cart made the toy fall off the back; stopping the cart suddenly made the toy fall forward. We discussed the usefulness of seatbelts.
Finally, we wrapped up with The Happy Scientist: Newton's Laws that demonstrates all three laws in one activity. You do not need a subscription to view this particular file, but I highly recommend it. For $20 a year you get a wealth of videos, experiments, and science information. Robert Krampf does a great job, and many of his videos are quite funny as well as interesting and informative. All you need is a bathroom scale--the type with an analog display (digital won't work)--and a heavy object (hand weights work well.) The kids are fascinated with how the scale changes as the weights are rapidly pushed up or pulled down. Simple yet impressive!