you wont find much overlap between hiking clothing and ski clothing.

I usually ski in just light polypro long johns, polypro sock liner, lightly insulated ski pants, a light wt 1/4 zip synthetic longsleeve shirt (LL Bean "microfleece" from 20 yrs ago) , helmet, and a waterproof/breathable shell. Even then I need to ventillate to cool down often. There is no such thing as waterproof and breathable when skiing for me, I need pit zips. And good waterproof mittens, my fingers are happy happy with mittens. Had to quit to warm up before with gloves when my hands would feel like in danger. Took me 10 yrs to switch and I was so freaking happy afterwards, hands were usually too hot. Bring a neck up in a pocket, but dont use unless gets stormy and really cold.

Depends on how athletically you ski though, YMMV. I never bring any additional layers skiing in bounds, and find a pack to be just really unnecessary and a drag to bring along in a resort unless need for carrying skis while hiking or carrying trekkers, etc. Kids cheap ski gear is over-insulated if they are athletic skiers too, they will be more in danger of overheating than needing any additional layers.

Todays rental boots are pretty good Im told, they are a hybrid. I have my own so dont know firsthand, but wife and kids never complain, and my kids ski expert terrain with me. Boots are all about a snug fit that transmits foot movement to the ski, without creating discomfort. The higher the level of skier, the more important boots and fit become. Elite racers may have their boot shells ground out for every toe inside as part of customization of fit. What you DONT want is to have to tighten the buckles too tight to get that tight fit, esp across instep as it will reduce circulation and fee will get cold. Thats where boots today with injection molded liners are worth their $$$$.