Our family loves an outdoor adventure, and the weather (and terrain) in New Orleans doesn’t always allow for outdoor fun. We have twice visited the Clark Creek State Park to hike and experience the waterfalls.
It’s about 2 1/2 hours drive from Greater New Orleans, located North of St. Francisville, right over the Mississippi line. Both times we have visited, we stayed overnight in St. Francisville and made a little weekend getaway out of it, but you can certainly drive there and back in a day. 
The hike does include some inclines, so it’s important to be in good health. But, my toddler walked most of it himself with a little help, so don’t be intimidated by the journey. We make sure to pack lots of water and sunscreen even though most of the walk is shaded.
On our recent trip, we were out there for about two hours (one hour in and one hour back) because we visited three waterfall areas. You can keep walking / hiking beyond that, but that’s usually enough for us. The waterfalls were lighter on the water flowing when we went early October because of how dry the weather has been, but there was still flowing water and shallow creeks to walk through.
The kids have fun climbing the stairs, climbing over large rocks, and walking along the creeks. I recommend walking in tennis shoes and then switching into water shoes to walk along the creeks and waterfall areas. You’ll want to return back into tennis shoes to return back to the beginning. (We brought one backpack with a change of shoes and a small towel to dry off.) We also like to bring a second soft-sided cooler backpack with water bottles for everyone. One trick is to fill an empty water bottle with creek water and use that to rinse off the sand off your feet before returning back into your dry shoes. 
The path is pretty well marked and you can opt to just visit the first waterfall and return back to the beginning. Sometimes there is a snowball stand open at the entrance for a refreshing treat when you’re done. We also keep additional cold waters and snacks in our car for the return drive home. St. Francisville also offers some great local dining, and we like to visit the Francis Southern Table and Bar for their Boudin Balls and other delicious menu options.
Other items of note: There is an honor system for paying the day use entry fee of $2.00 per person with children five years of age and under free.
