Hartford has two train stations, one on the Liverpool-Birmingham line and one on the Chester-Manchester route. You could live anywhere on the Chester-Manchester line and your boys could easily get to the Grange.
Delamere is a gorgeous village. It's closer to Chester than Manchester and would be a bit of a trek for MGS, but is only a 27 min drive to Kings Chester which is a similar sort of establishment.
Then on the other side of Northwich there's Hale, Knutsford, etc.- a bit bougie but nice if you like that kind of thing. It's not unusual to travel from Knutsford to the Grange by train.
Northwich is not rough and the town centre has actually changed a lot. 15 years ago, I would have agreed it was an absolute dump, but the council have put a lot of work into revitalising it and now there's a cinema, a decent leisure centre with a theatre, a few nice bars and places to eat, the river has become more of a focal point with dragon boat racing and the river festival, and other events throughout the year which give it quite a nice sense of community. I wouldn't rule out Northwich and it's surrounding villages.
If you're into walking and the outdoors, there's a lot of options- the Anderton boat lift and Marbury park with lovely canal-side walks in between, and Delamere forest.