Staying in Newtonmore for a week, any reccommendations for a good Munro / hill to do with the kids?

I presume you mean on foot?

Meall Chuaich is pretty straightforward with a good track in and then a short ascent.

Otherwise, Cairn Gorm. You start fairly high on account of the ski area car park and there’s a track all the way up via the Ptarmigan (where you can sign in/out to use the facilities).

Meall a’ Bhuachaille is the hill “opposite” Cairn Gorm across Loch Morlich and is less of a climb but actually has better views as you get the view of the Cairngorms 🙂

How old are the kids? The A9 munros are not the most interesting in summer, but are amongst the easiest walks with the high starting point. So if the kids are very young they’re worth considering for practical reasons.
We did A’Bhuidheanach Bheag, the one to the east of Drumochter, with our kid when he was about 2 – so a mix of him walking and in the backpack. Worked great and was a nice length.

If the kids are older than look to the Cairngorms – or there’s a couple north of Loch Laggan that are meant to be very good (haven’t done them myself – is it Creag Meagaidh that’s the popular peak round there?)

yes, on foot.
Bikes will be taken for other days and I know plenty of good biking routes.

Kids are 12, 10 and 4. I expect to carry the 4 year old for some of the climbing.

If the kids are like my son was when he was younger then they might appreciate a route that’s a little more interesting than a big walk up and down a great big hill – which is what most of the hills off the A9 around Newtonmore are like.

Druidh’s suggestion of Cairngorm is a good one but have a look at ascending via the Fiacaill Ridge – only if you and the kids are confident with heights and a bit of scrambling. The scrambling involved is easy (by-passable on the right to avoid exposure) or more challenging if you want it so. It’s quite easy to see where you are and where you move next.

This makes the route a circular one, gives fantastic views of the northern corries and makes for a memorable day. It only adds a little extra ascent from Coire Cas ski centre and you can stop at the cafe below the summit and get a ride back down on the funicular railway if the kids are tired.

Although it’s only a short distance from the top of the Fiacaill Ridge to the summit of Cairngorm, it does require navigation skills if in mist.

cheers all, I have the OS maps of that area and am confident in navigation so that is no problem.
We have tesco clubcard vouchers for a trip up the funicular so would prefer to walk something different.
Something with a bit more interest than a wide path up and down would be good too.

Geal Charn is close and dead easy (start @ Balsporran cottage 6 kliks South of Dalwhinnie)

Carn Liath (start Aberarder North shore of Loch Laggan) also close by.

Meall a Buachaille is a good shout as a circular (tho not a Munro)Start @ Glenmore Lodge then Ryvoan, summit and back down it’s SW flank