Northern Queensland to Darwin

[nevpen]

we are a family of 4, kids aged 10 and 8. Last year we purchased a yacht in Sydney and sailed up the coast to Townsville where she is now on the hard. We'll soon be heading back to Townsville to set off again to Darwin and looking for suggestions on what to see and where to stop. Weve got about 5 weeks.
Im particularly interested to hear of suggestions for a great spot to stop on the reef for easy snorkelling for the kids. We didnt make it out to the reef when we sailed the whitsundays last year so want to make sure we get there this time.
Any suggestions for the best places/islands to stop would be greatly appreciated.
From Darwin we will make our way through the Kimberley back to Perth which is home. We are really looking forward to this part of the trip, having done it 12 years ago pre kids!
Look forward to hearing any suggestions
Cheers