In reply to Lynsety:
You will be lucky to find anything for half term now, but most places are on Google, booking or Hafjells own website.
Try elsewhere like nordsetter or sjusjöen, not so far from lillehammer. Further away, kvitfjell and skeikampen on the same lillehammer valley pass.
The best place partially depends on the age and ability of the kids. If they'll endure a full day or need other non skiing activities to help tired legs recover.
Post edited at 13:20