Welcome I'm in same boat, still a noob. Listen to these guys they are great.
I dug up my 30 year old tyco supply etc that still works but gave up on it and the old brass track Tyco, Atlas and flex etc.
I'm reusing my old rolling stock and buildings though.
I'd suggest Bachmann EZ track nickle silver HO scale. Heavan compared to the old stuff, most hobby shops carry it.
May consider getting a bundle from thefavoritespot on ebay
http://stores.shop.ebay.com/THE-FAVORITE-SPOT
or
www.trainworldonline.com.
Other folks may have other suggestions.
F7 diesels seem to be best kid proof engines.
My 4 year old is great, my 2 year old needs watching LOL
I'm, running my 30 year old Tyco Santa Fe F7A too after alot of cleaning and lube.
I got a lifelike set from toys r us for $60 at xmas but switched to NS EZ track. I let the kids play with the Tyco and Lifelike stuff and only watch when I run the new Bachmann trains. (good bang for the buck)
Seems everyone ends up withh DCC, I'm still DC only but slowly expanding with DCC in mind.
It all gets way too expensive very fast so take your time. Lots of fun, lots of resaech, lots of mistakes LOL
http://www.nmra.org/beginner/
Cheers,
Richard