Yeah, it is quite popular with kids over here as well, England, you need to keep an eye on the Hornby range, they do a large range of Thomas stock and accessories. The only problem you may have is that it is to the British 00 scale rather than HO, this makes it slighter larger but taking into consideration that Britain has a smaller loading gauge and smaller stock, the difference is not too much.
There are a few really great OO/HO scale Sodor based layouts on the exhibition circuit so should be a few on the internet as well, try Googling it for ideas/examples.
Best wishes and have a great Christmas.