Some of the upper floor WL rooms that face MK have a view of the high fireworks, but there's not really a view from the beach.
There's much better views from the beach at MK, the boat dock at GF, or the two observation decks on the top floor of the Contemporary (this had been limited to California Grill diners, but have read that it's been opened up to everyone again).
You could take the boat to the Contemporary from FW and then take the same boat back to WL.
Not sure if there will be any difficulty with you wanting to leave the care at WL for that long. Some resorts issue the 3 hour parking card and others don't seem to care. If you can't view the fireworks from WL, perhaps you just want to park at FW. The Contemporary is definitely a resort that questions guests who want to enter --- perhaps to avoid people parking there to walk to MK.