Aero or Funen Island


My family (grandparents and toddlers included) are visiting Denmark this August and I'm planning the itinerary for our 8 nights visit:

3 days in Copenhagen

1 night in Aarhus

1 night in Billund - legoland

And then was wondering whether to visit Funen or Aero islands for 2 nights. Open for other suggestions.

I am considering taking a flight in between (Aarhus or Billund) to make it easier and less driving in such a short period.

Suggestions please!