It is my favourite park in Paris and you can easily spend a full day with your kids here.
It is so much fun, even as an adult, to rent one of the little sailboats in the main fountain of the garden and push it around with a stick. Most of the time it capsizes or collides with another boat, but that is part of the fun! (You can rent the sailboats on Wednesdays and on weekends.)
They have lots of different boats to chose from and they are all made from real wood.
The playground there is fantastic and even though you have to pay for it – it is the biggest playground in Paris I know! An extra plus: toilets for the little ones and changing tables, not that normal in Paris especially not in a park.
On Wednesdays ( on Wednesdays french kids have only a 1/2 school day and the afternoon is free) and week ends you can send your child on a pony ride. They have those big double seat (where you face each other) swings as well.
And of course you will find one of those beautiful old style Manege with wooden animals to choose from.
Take a break with a croque monsieur and a bottle of Orangina in the Parks cafe.
Please go to Jardin du Luxembourg when you are in Paris and spend a day with lots of fun and french style.