We've been to Copenhagen before and we absolutely loved it. Now our kids are a little older (will be just 8 and almost 6 in the summer) we are going back to get more out of the Tivoli.
Last time we had a toddler and a baby and did the Tivoli, the zoo and the science museum (Experimentarium). We had such a great time I am quite tempted to just do the same again but now we have 4 whole days rather than 3 so we can do one other thing at least, or skip some of those 3 to try something new. We prefer to do one 'big' thing per day and then fill in the edges with wandering, ice cream, hot dogs, playgrounds - we're not trying to cram too much in.
We will definitely do a day in the Tivoli, but what are the most fun things for a family with primary age kids? It'll be July, so busy peak season but hopefully pretty good weather. What about the aquarium, is that worth it over the zoo?