I would consider that to be the same location, so definitely less than 150 miles apart for me. Try riding around towns a bit. I bet there's a car dealership with some balloons tied to at least one of their cars. Or one of those party stores, like the one you'd buy balloons from, that has a few Mylar balloons outside. (I bet you can see a car dealership with both a flag and balloons from the interstate.) Or a house with some left over balloons tied to the mailbox for a birthday party a few days earlier. Or a neighboring city that will be doing fireworks for the 4th. Or some kids doing fireworks in the yard.
That feels more in the spirit of the ride to me. It adds a bit of challenge since you are on a small scavenger hunt, and it should make the ride more enjoyable. If you're doing an SS1K, you'll have plenty of time for finding suitable photo options. Make it a fun, memorable ride! Sometimes taking a picture of a kid's coolest 50 cent firework is a better memory than the city's big firework display.
Then again, maybe I'm biased. I'm currently planning a big long ride and extending it a bit both in time and distance cross a few items off my bucket list. Don't let me tell you how to do your ride.