I am not aware of much agate in Delaware, so I doubt they are agates. One would need to smash or cut them open or polish a part of them to get a proper ID since they do exhibit the river tumbled "frosting".
You might try putting a little mineral oil on the surface as it might give you an idea of what it might look like polished. Sometimes this works very well...other times...not so much.
I remember when I was a kid, I'd be rock hunting with my Dad. We'd be looking for agates or what ever, and if he needed a shiny spot to see what the rock looked like, he'd lick the rock. I never could get with that program.
I would tumble the first two on the left, on the first picture, but not an expert here, lol. I tumble only river found rocks and the result was pretty nice so far, after 2 batches. You're right BosnMate, licking color on a stone will get an idea of what it could look when polished.