My other two bit of advice, which may be less useful if you are riding as a family, are:
(a) Find some like minded people to ride with. Mountain biking is a very sociable sport, so it is easy to fall in with ‘the right crowd’ who will help you learn and help you tackle things you did not think you could manage.
(b) Get some decent lights and try night riding… it’s great fun; it expands your options for riding in winter; and for the kids (OK, for everyone) it’s an adventure. If you go for ‘18650’ torches rather than purpose MTB lights then all you need one £5 charger, a then a couple torches with mounts and cells for each one of you… and a 501b XM-L2 torch is under £10 these days.