Any hotel in or near the Vila Mariana neighbourhood will give you great access to the Ibirapuera Park and its many family-friendly attractions.
Rent a bike for the day inside the park and explore gardens, woods, museums and buildings designed by Oscar Niemeyer.
After dropping off your bikes, walk up to Paulista Avenue for a taste of Sao Paulo culture. MASP museum is a perfect place to start. Work your way through towards the Paulista Shopping Mall and just a few blocks ahead and you are back in Vila Mariana. The circuit might take a few hours, so remember the sun cream, hats and water please.
Another interesting family sight-seeing experience is walking towards Liberdade instead from Vila Mariana. This is the Japanese neighborhood and ideal for a meal in one of the many traditional restaurants.
From there, head into Sé Square with its beautiful cathedral, down to Sāo Bento Monastery and on to the Mercado Municipal. Beautiful tropical fresh fruits and freshly made cold juices are sold in there, great to re-fill those bellies.
Then take the tube back to the hotel as the walk back might be one too many for the day.