Hi i have done a lot of research this year and have followed the companies checking prices daily etc!
Nearly all research suggests avoiding a day trip if possible - it's a 3hour flight with 2 hours airport either side which means for about 2k you will only get 5 hours there, less if theres any delays. If you monitor prices right you can get a 3 night break for about the same price.
I have booked 3 nights in saariselka with thomsons on the 16th for 2 adults and 2 kids for £2208 - booked in June. Since then I have been watch I prices every few days hoping that they don't reduce as I wasn't sure at the time whether to book!
Anyway since then prices have altered dramatically and at the moment they are the highest they have been since may! Certainly do not book now as I expect they'll drop closer to the time. I think it's peak time at the minute.
If you can fly Gatwick try crystal ski as they have some good Santa offers which I would have booked but we flying Manchester. Esprit are meant to be very good but much more expensive.
If you can, stretch to the longer trip as most day trip reviews are poor because it's so rushed and kids get exhausted. Thomsons have rovaniemi going for 3 nights for family of 4 for about £2250. You will be unlikely to find any stay trip for under £2k unless you book within a week or 2 before. Last year they we sill over £2k at the end of November as I checked then too!
The prices for day trips haven't changed at all over the months and are between £1700 and £2k for family of four so not much different to a few days!
Inghams, thomsons, cosmos all go but do check itinery as they vary not only by operator but also by resort within the same operator!