Spending a week in Stockholm where my dad/step mum are living right now. Would like some child friendly ideas to spend as they are only going to be there for three days then letting us stay in the flat, so we've got four days without them. Three DC 3-9. 
Going to go to Gamla Stan and the Nobel Museum with DF/DSM. Thinking of seeing the Vasa and the Nordic Museum too. Where else is fun and family friendly?