I swear by silk gloves (and silk socks). Ds (7) even has a pair, even though they are too big for him and they made a big difference to him last year. (He didn't need them this year as the weather was fabulous - although I always wear mine, no matter waht the weather! )
I got him the samllest adult pair, which, 'cos they are thin, are OK within his mittens. At that age, I would recommend getting good ski mittens (rather than gloves) which are on a string. That way, when they are out on the mountain in ski lessons, yuo don't eed to worry about your kids losing them.
Another vote for TK Maxx, especially for salopettes. Trespass jackets are great value: if you can find one of their three-in-one jackets, then you will be able to make maximum use of them after your holiday.
Don't know about Austria, but where we go in France, the good ski schools wil only take 4-6 year olds for 2 hours a day. We then put ds into the "Ski Creche" (run by the french Ski School) for the afternoons which involved more fun in the snow and a wee bit of skiing.
From 6, the ski school we use will take thme for 4 hours a day 9with two full days) - but be warned: they can be very tired after that.
You'll need to go into ski schol yourselves - and will probably also be axhausted, so you may well find that all you want to do afterwards is have some lucnh and then crash out!
I really would recommend a few lessons beforehand for all of you. That way you will make the most of your time on "real" snow. You can either go to one of the X=scapes or Snowdomes or to an articial slope. I have never ski-ed on an artifical slope, but I am told that it is an excellent way to start, as you can learn the basics - and then, when you get on to the "real" stuff, it is soooo much easier I have been to Xscape, to help ds get his snow legs back - and the snow there is good - but it is expensive.
FWIW, dh only started learning to ski when he was 34. We then had a gap of three years, but once he started again he became abosultely addicted. He is now 48 and is an excellent ski-er.
We are both really jealous of ds, who started at 4. He is now skiing confidently down blues and easy reds - and at times I have to stop skiing gently and start skiing hard to catch him up!