EP will speed things up considerably for you. Keep in mind that Hagrid’s, Velocicoaster, and Pteranodon Flyers do not take EP and the lines can get really long, especially Hagrid’s, so plan accordingly.
Another place your EP won’t help is with crowds in the streets of the Wizarding World. If your kids love HP, they will want to buy a wand (either by getting lucky and being picked for the wand ceremony or just buying at Ollivander’s), and work the magic windows. On crowded days, people will line up at the spots. You may have to wait for 5 or 6 others to do the window before it’s your turn. It’s not a huge amount of time at each spot, but it does add up if you want to do all/most of them. It also loses some of the wonder of it when you’ve already watched other people do the illusion multiple times.
Take advantage of early park admission for sure. And getting there at least an hour before the EPA opening time is key to being at the front. If you are near the front of the IOA line, go directly yo Hagrid’s. If you’re not near the front of the pack, don’t bother - the line will be ridiculous and you’ll waste your early time waiting in that one line. Instead head to Velocicoaster if that’s of interest (it can move a lot of people through so lines don’t get as bad as Hagrid’s which has a lower capacity). Or use the time to get a wand and do windows while most people are running for rides.
Honestly, if you don’t get there early enough to be at the front of IoA for Hagrid’s, you might be better off going to Studios, and spending that time doing the windows of Diagon Alley. That area is much bigger than Hogsmeade, and you can do a wand ceremony, buy a wand, and get through a lot of the windows during that first hour when the crowds are low in the streets. If your kids really want to do Harry Potter stuff, this will be the best time for that.