Family short break to Scotland

[VTECMatt]

I'm planning a 3 day break in a couple of weeks and have no idea where to go, was thinking Loch Lomund or Arran. I have never been to Scotland in my adult life and since moving to Cumbria this year more accessible. Taking two kids 6&7 mother in law and wife.

Suggestions on where a novice visitor should visit and stay. Don't want the cities.

Tia

Matt