on the button straddle

$50 or so in the pot on the flop, turn adds another $45. Average stacks around $300.
If the turn is low then go $10. You need for somebody to have a hand at this point but you can't expect them to go broke with it.
As the turn card gets better bet more, up to $50 for A/K. You will probably fold out some low pairs but they are not putting much in anyways. Better to bet big and hope somebody made a good boat and will put in a lot.
This is a situation where having a read matters a lot. If somebody looks like they thought about betting then go bigger. If everybody is checking waiting to fold then go smaller. Just don't check. If nobody else has a hand then go ahead and end it. It's a mistake to try and nurse another small bet when you have a huge hand.

Honestly I think the $5 bet looks more suspicious than just betting $10 or something more in proportion to the pot. I would typically bet super small with air, and then size up on the turn to fold out all the other airballs that floated the flop. With value, I'd size up a little on the flop, and then just go a little larger on the turn.

So, bet $10 on the flop, and $20-$25 on the turn. Just keep laying opponents insanely good odds to continue.