Hemsedal is lovely - plenty of easy runs for beginners and all the instructors speak English. A very chilled place, but it can be colder than in the Alps.
It is also different from the Alps in other ways:
Much of the accommodation is self-catering, and food in the shops is expensive. (it is hugely popular with Danish families who drive up with a car-load of provisions for the week).
Speaking of Danes, the Danish school holidays are Week 7 (from Sat 8th Feb) and Week 8, so these will be the busier, more expensive weeks.
It is not a "party" destination - which with a small child is probably not an issue, but be aware that after 4pm the place gets very quiet. Apres ski isn't a thing and people go back to their accommodation, not to emerge until next morning.
It also doesn't have the cosy mountain restaurants or huts with terraces that you find in the Alps - the food in the main restaurant at the base station is very good (great fish stew) and there are tables where you can sit with your own lunch-pack which helps to keep the cost down.
Oslo Airport is stunning - you look at it and think "why the can't Stansted or Manchester or Birmingham look like this (instead of looking like glitzy shopping malls with a shitty airport attached).