I first took my children to the lakes for a kindy outing some years ago. We all met on the Dutton Park side of the Green Bridge, then scootered and cycled across the bridge to the St Lucia campus of the University of Queensland.
Just beyond the end of the bridge lay the lakes: two or three sprawling pools surrounded by green lawns and populated with happy ducks swimming about.
On the kindy outing, we all enjoyed a picnic on the grass, then went for a walk among the spreading trees that edge the lakes.
This is stil one of my favourite things to do. It's always pretty and relaxing, and young children can have lots of fun watching the ducks swim around. You can usually find a mumma duck and her babies, and there are often other bird species as well, including dusky moorhens with their bright red beaks, and big, fat guinea fowl with their beautiful plumage.
If you don't want to pack a picnic, you can also buy food close by. Just head up the hill from the lakes (a five-minute walk) and you'll come to the university's refectory, which sells a range of food at reasonable prices (ranging from quite healthy to the usual hot chips etc).
If your kids are up to walking another minute or two, you'll find yourself in the Great Court, a green lawn enclosed by the university's older sandstone buildings.
It's a beautiful space, and also home to a Merlo's, where you can buy good coffee and a better class of food (though more expensive than the food at the refectory, and possibly less child-friendly, depending on your child's tastes).
They're also very easy to reach: you can drive to Dutton Park and head over the Green Bridge, catch any one of a number of buses that pull up right beside the lakes*, or catch a CityCat to the university and then walk about 10 minutes to the lakes.
Whichever way you get there, I think you'll find them a pleasant and scenic surprise.
*Make sure you get a Lakes bus, not another UQ bus, as the others stop at a different bus station at the other end of campus -- about a 15-minute walk to the lakes if you have kids in tow.
PS While many families used to feed the birds, signs have recently gone up asking visitors not to engage in this activity. The birds are much healthier eating a natural diet, and feeding can make them aggressive. If you do visit, please follow the university's rules, and teach your children why it's better not to feed any wild animal.