|Your kids' version of Sant'Antimo will look much more interesting than this
You can find the monastery's silhouette on the Facebook page of Siena's tourist office. Once colored in, scan your kids' take on the famous Romanesque abbey and share it on their page. But what do I say? Forget the scanning. They probably know how to do all of it straight on your iPad.
There are more silhouettes to download for the rest of your trip through the province of Siena: the skyline of Siena during sunset, a lonesome farm in the hills of the Crete Senesi (or maybe it's already the Val d'Orcia - not sure), a Maremma shepherd dog and his flock of sheep, the famous group of cypress trees near San Quirico d'Orcia, a medieval stone bridge (no idea where it is, but looks great) and the silhouette of San Galgano abbey, the famous roofless church. You can find all of them here. Just click on scarica to download the pdf file on your computer.
Before coming out, you may also want to check out my post about Sant'Antimo and Castelnuovo dell'Abate. No coloring in, but find other great stuff to do when visiting Tuscany with children in tow on Map It Out's Siena for Kids and Fun in Southern Tuscany with kids pages. Or just take them for a walk. That normally works with mine.