If Courchevel 1850 is the smartest address in the Three Valleys, Méribel is the friendliest. It has been the British family favourite in the French Alps for decades (the resort was actually founded by a Scotsman, Peter Lindsay, in the 1930s), and the British presence is still notable: chalet companies, ski instructors, restaurant staff, half the families on the chairlift. For a first or second family ski holiday, this is genuinely an advantage. Lessons can be booked in fluent English, the kids' clubs are run by people who understand British school holiday rhythms, and you'll meet other families to ski with by Tuesday.
What makes Méribel work for families specifically is the combination of factors: tree-lined runs (most of the skiing is between 1400m and 2700m, so you get proper trees most of the way down, which makes a huge difference in poor visibility), wide and forgiving pistes, a village that is laid out along a single road (so you can walk everywhere), and full access to all 600km of the Three Valleys via the Saulire and Tougnète chairs. You also have the option of staying in Méribel-Mottaret, slightly higher up the valley, which gives you a more snowsure base and arguably even better access to the wider area.
Where Méribel gives a little ground to Courchevel is in the very-top-end accommodation (there are some superb chalets and hotels, but no equivalent to Cheval Blanc or Le K2) and in the fine-dining scene (good, but not three-Michelin-stars good). For most families that is exactly the right trade-off. You are paying considerably less than Courchevel 1850 for what is, on the snow, the same skiing.