From my experience - kids can't stand long lines for rides and unlike most adults they just can't stand it. What we used to do is to bring fun stuff so we can enjoy something while waiting in lines. It can be cards game like TAKI or anything that may be usable during lines.
My second tip concern the "I want this... and this ... could we please buy that one ... " The souvenir shops desgin so kids and adults won't be able to resist those items. Even as an adult I found myslef buying and buying in Disneyland stores. Although it is good to let kids get used to take NO for an answer, it can ruin the day in the park for everyone, so the trick is to give them the money they can spend before so they can control their shoppings and wont be able to cry when they spent it all.
Always take an extra shirt for the littleones. Water rides mayb be fun for big kids but most little kids hate getting wet not to mention staying wet. I remember being with my niece in a park having a blast till the splash ride. She was abut wet and was so unhappy we had to go home an hour later as it wasn't anymore fun for her or for me.