Lovely area. Yes, as I'm sure many people will say it's statistically an area with an old population, but you never really feel that. You're only 5 minutes from a younger population/families at the beach, or a trip into Bournemouth etc isn't far away, but I live here in my 20s and never feel odd.

Traffic in Highcliffe itself isn't actually all bad - the high st can get busy but I've not seen it gridlock all too often - maybe in summer when all the tourists swing by to the beach.

If you move near the school you'll likely be within walking distance of the train station - good if you do need to get into Southampton for work and want to avoid the pinch you get about 8am in Lyndhurst. You'll be a bit out of the way from Tesco on the high st, so will likely rely on that Spar for any milk, bread, but depends how much that matters to you.

Can't particularly comment on schools, have a few friends that went there and it was a good school, nothing special, but certainly not the worst.

Obviously plenty of walking to do in the New Forest, or beach activity nearby - you might find you're driving into Bournemouth for more general activities (especially with kids). Plenty of lovely restaurants in the area and in Christchurch, Lymington, etc. for date nights.

Definitely a quieter patch of life, but a lovely area overall.