Travel In Portugal

We visiting Portugal for Christmas and New Year with some friends...kids as well (between 11-14 years old) Can anyone recommend must see/do things for us?Two things we absolutely want to do is to take the kids to go see snow...I know it does not really snow in Portugal but we are thinking of a ski-resort...any recommendations?  Then we would also like to take the train trip from Lisbon to Madrid....any suggestions on that will also be appreciated!Thank you!!