I would just take a long break but not two. I will probably not be in the parks super early unless the kids are up...ie I will not wake them. And then stay until just after lunch. Then we'll go back to the hojo and possibly swim and then nap. My kids usually nap for a at least 2 hours. Then we'll relax a little (depending on the kids) and head back to the park. I am not expecting to just hang in the room with two little ones but I am not going to rush anyone either. I expect to be back in the park around 5. Fireworks are at 9:25 so we should make that. I def dont expect to make it till closing, and may have to watch the fireworks from our room, but we'll try. Just gotta follow their lead.
If you do want to do 2 breaks then I dont see an issue with it other than I would probably go back for the 2nd break and decide not to go back to the park lol Just do what is right for your family. Perhaps try it the first day and if it works continue to do it?