Traveling with Kids to Rome? A few (seriously) off-the-beaten-path sights

After you've seen the Colosseum and a few other choice spots in Rome (live links to most  colored words in post) what else do you do with the kids?  Of course, there are the usual suspects, like Explora or the Rome Zoo (Bioparco).  But, after a friend took her son all over northern Italy, between boat rides on Lake Como and rollercoaster rides at Gardaland, he called me to tell me that his absolute favorite part of Italy still remains Villa Borghese.  Villa Borghese?  The place you go for long walks with your fidanzati? Turns out Villa Borghese with its Segway rides, go-carts, golf carts, rowboats and little trains is a child's fantasy land. My sister's kids hide secret clues in tree trunks there for other kids to find (through the Letterboxing website).
A little farther afield at the EUR off the via Cristoforo Colombo you can find a larger lake with pedal boats to rent.  Nearby, just behind the ex-Fiera di Roma there is a Police vehicle museum.  Go past the cool catacombs off the via Ardeatina and up the road a few kilometers is a nursery - housing buggies & other vehicles of all kinds.

But today I came across a strange place, if you happen to have some time to kill at the airport.  In the cargo area, where the Fedex offices & National Car Rental are, we sighted a gigantic megaphone situated right in a field.  Coming closer, we found an entire graveyard of old county fair exhibits: a Trojan horse, the Columbia space shuttle (which looked like it had truly burned upon reentry), a bigger-than-life dirt bike, an abandoned ship.  It was magical, and if it'd been in the USA, they probably would have been totally revamped for kids to romp upon them, and ticket booths wouldn't have been far away.  It was a bizarre trip through the Land of the Giants.

But if you have a few extra hours and your rental car, a trip to Capalbio - just after Civitavecchia - is always a pleasure.  There, if it's your lucky day and you actually find it open, you can visit the Giardino dei Tarocchi - the Garden of Tarot cards growing from the imaginarium which is the creative mind of French artist Nicki de Saint Phalle.  For more strange figures, there are the creatures in stone of Bomarzo, also outside Rome. 
Still outside of Rome, there's also the new Cinecittà World amusement park - MagicLand & other parks & water parks.  I believe Cinecittà movie studios still runs tours there, as well.  
While looking into Underground Rome, you'll find some cool sights to see - but I was especially intrigued by the tours offered in Orvieto. And, finally, there's Ostia Antica - Rome's Pompeii.  If you're lucky, you might even find a boat ride there.