I am so jealous, we can't afford to go this year (or last year either)
February is great for most European resorts. I would be tempted to give the Thomson type ski packages a miss, but would recommend phoning a company such as Esprit Ski as you are traveling with children. Phone, don't just look on the website and they will give you good advice and good prices (we always found they came out very comparable with the Thomson type package companies) Mark Warner is also spoken very highly of, but it always seems more expensive.
Catered chalet is the way to go with children. Esprit and Mark Warner both have some with built in childcare options which are useful even if you just want someone to listen out for your sleeping children whilst you have a drink in the lounge.
The best ski holiday I ever had was a package ski holiday to Romania.
I've also ski-ed in Austrian and Andorra, but Romania was just great. Relatively inexpensive, fun, friendly, brilliant landscape and history (Transylvaina), lovely easy and intermediate runs and the most bonkers nightlife.
I met people there who also said Bulgaria was good.