Hi Susan!
Thank you for visiting the Moms Panel!
What a wonderful place in which to celebrate your son's 8th birthday!
On July 4th, the fireworks at the Magic Kingdom park, '
Disney's Celebrate America', are scheduled for 9.00pm. You can see these very clearly from the beach at Disney's Polynesian Resort.
There are two show times for Spirit of Aloha: 5:15 and 8:00. The show lasts about two hours..
You will miss the fireworks if you have the 8.00pm reservation, but I have just checked the website, and there is (as this moment) some availability for the 5.15 show on 4th July. If you wanted to see the fireworks this would be your best choice. You could spend some time at the resort, after the dinner show, enjoy the surrounds and pool area, and find yourselves a good viewing spot on the beach.
If you have any other questions, please come back and ask me - I would be happy to help you plan your magical vacation!