Need help with a game and toy.

I have 7 grandchildren all are 6 or younger. The 3 oldest ones just LOVE trains. I am trying to find a model train simulation for the PC. The only thing I can find is Model Train Simulator 2011. I dont want a game where they drive the trains. I have those already. I want a game where they can build their own model train layout and scenery and then watch it move through their design. Anyone have knowledge of the above mentioned game or perhaps one I dont know about? I can't really find much info about one.

This looks like something they would absolutely freak out over. Has anyone seen this or actually tried one? I mean I'm not gonna pay 2 bills for one, but I would love to know how this thing actually is. Again, limited info I can find on it.

http://www.ebay.com/itm/Pre-Sale-Ta...788445?pt=Model_RR_Trains&hash=item5d3c6dd11d

I think Sid Meier's Railroads has a sandbox mode that's pretty model trainish, but don't quote me on that.

I believe kids that love trains would adore Rollercoaster tycoon games (cheap on GOG).

Also this game should do the trick too:
http://store.steampowered.com/app/65710/?snr=1_7_7_151_150_1

I have the rollercoaster tycoon games. Still a bit too young for those. The ages are 6,5,4,3,2,2,1 (I also have 2 grandchildren in Hawaii, a boy and a girl. I have seen the boy twice, and have not met the girl yet, but that's a different story.) They all just love to watch when I play the train sims. I think they would seriously love a game where they can build their own railroad.

Thanks for the link joxer, but that's not what I am looking for. I have the Trainz, and Train Simulator and tycoon games. The simulators are way too complex for them yet, although I think they will love them in a few years, as long as the interest in trains holds up. With kids, who knows. By the time I find a game, they may love dinosaurs by then. If I find the Model Train Simulator 2011 cheap enough, I will give that a go.