First, we lay down on the basketball court and outlined our bodies in sidewalk chalk:
This is terrific fun in itself, because you can measure them and compare them and stomp on their heads, etc.
You also have to have with you a very good dinosaur encyclopedia (we have four). A good dinosaur encyclopedia will give the length of every dinosaur, and will either give its adult height, or will show a small picture of it next to a person outline so that you can estimate its height. With that and a tape measure, you and some kiddos can measure out the length and height of a dinosaur (don't even try to do a diplodocus, though--it's almost as long as a football field).
The girls wanted to do a T-Rex--about 40 feet long. Definitely do-able.
I turned the actual T-Rex drawing over to Matt--he's so skilled, and I'm so not, that it just seemed ridiculous to muddle through it myself, but if you're not super-skilled at drawing, yourself, you can also make yourself a big grid on the basketball field and a small grid over your picture, and copy--but I brought our artist's chalk set so that the girls could decorate their own chalk outlines while Matt worked:
This turned out to be such an awesomely fun activity in itself--
--that I imagine the girls and I will go back often to the basketball courts just for this.
So after your artist-in-residence has finished his masterwork, you have yourself a life-size drawing of your dinosaur of choice for your girls to explore. And the girls...well, the closest that I can get to a description is Glory. They gloried in their life-size dinosaur drawing:
Sydney ran around and around and around and around it, but after a while Willow just had to lie down in an ecstacy of happiness and just simply wallow:
I was thinking that you could probably do this same kind of activity with all kinds of things--sea life, trees, cars. How awesome would it be to draw a life-size picture of your house, or a blueprint of it that shows all your rooms and your furniture?
But you could leave out all the junk that's all over the floor, probably.