There is plenty to do in the winter espesially in the snow! You don't have to ski as there is plenty on offer.

Sledging, Tobbogganing, Hiking, Snowball fighting, Snowperson making, Climbing and much more!

Both Turoa and Whakapa (the two ski fields) are operated by the same company so you can check out deals for rentals, leasons and lift passes online here. Note they do have packages for beginners. By the way you can also purchase your passes and rentals in Ohakune but check with driver as can take a while to sort out.
If you simply want to have a look around I recomend the sightseeing lift pass for $26. This is return lift pass up the mountain so you can check out the view from higher up and there are more cafe's as you go up. The lifties will help you on when you get there. They also have more info for first timers that may help further here.
Best you ask around when you get there on Friday night to see what other people are doing and who you can tag along with. Travel arrangments up the mountain may differ to getting to Raetihi. Most of the die hard skiers will be off early to catch the first chair but others may wish to take their time and leave at a civilised hour but basically similar abilities can stick together.

Ski gear,

The following is based on my time up the mountain and is not just what works for me but many others that ski with me.

You do not need to buy flash gear to have a good time up the mountain. A $20 PVC jacket block the wind the same as a $600 Gortex jacket. The difference is movement, comfort and style.

If you don't have any ski gear you can rent it from up on the mountain. http://www.mtruapehu.com/winter/Clothing-rental/

There are basically three things to think about with the clothing; thermal, wind protection and movement. 

THERMAL A good start is a snug layer of thermals against the skin. There are many options out there from wool to polyprops.  Follow this with a jumper and you have a great start. Things to note is AVOID cotton. Cotton when wet can draw heat away from the body having a cooling effect. Best to have first layer snug to trap and keep warm air next to your body.

WIND PROTECTION The wind can make it very cold for you up there so make sure your outer layer is a wind breaker. If you are not wearing it make sure you are carrying it.  There are plenty of options out there from nylon parkers to PVC Jackets to the big $ Gortex jackets. Not only jacktes remember pants as well. If you are going for a slide around play in the snow I recomend the warehouse PVC pants. I got some PVC/plastic pants last week for $18 at the warehouse and they will do the trick for sliding down the hill on my bum.

MOVEMENT I often see people with so many layers that they look like the michelin man and can barely move. Exercise warms you up so if you restricted by your clothes you won't benefit from this simple heat source. Also if you can't move you can't throw a snow ball so you end up the target and that gets old quickly.

Other things are you lose a lot of heat out of your head so remember warm hats.  Gloves are a must as falling over in icey snow hurts. Sunnys are a big must as there is a huge amount of glare off the snow which in effect doubles the intensity. This can cause snowblindness. I went with out sunnies for half a day and couldn't see for that whole night. Check they protect against UV. Following this I therefore suggests sunscreen. Shoes, Unless you are in ski boots or proper snow shoes I don't think there are many great options. What ever you choose will get wet. Again avoid cotton so thick woolen socks is a good start.  Also I heard that you are better with a rubber sole as synthetic sole are more prone to sliding on ice. 

Sunscreen not required here.

Ceroc Kapiti-Hutt 2013 Ski Trip
Friday 23 August through to Sunday 25 August
More details here