J.M.
Not sure there are discount tickets available for park admission. Be careful about buying tickets from others because you won't know if they are legit. My tip is for you, your husband, and your older child to bring a backpack with drinks and snacks. You are allowed to bring food in the parks which will save you tons of money. Bring water bottles that you can refill to keep it lighter. We would eat a big breakfast and then just bring snacks for the day and then leave before dinner to avoid eating any meals at the park. If you are staying close, you could leave the park in late afternoon to eat an early dinner then head back to the park for the rest of the evening since most of them stay open late during the summer.