Bench Joinery Help

Hi all,
I've searched the forum and posted in other places, but haven't quite found what I'm looking for. I'm hoping you all can help!

I'm building a porch bench for a friend out of barn wood from their property. The material won't be flatted or square. There are too many hidden nails and I use my company's planer/jointer which I do not want to damage. I'm mostly just sanding it to remove the rough surface. The material will be 1.5" thick and is some kind of soft wood.

I'm attaching the legs and spreader with a half lap and screwing through the top of the half lap to help stiffen it up. My plan from there was to either just plop the bench top on the legs/spreader and screw through the spreader in a few places. OR make a tenon that takes up most of the leg stock and mortise it into the benchtop by 3/4". I'm worried that it'll still rack. What you would you do to prevent racking?

I'd prefer not to move the spreader further down the legs. I'm aiming to have no exposed fasteners or brackets. Someone else mentioned they would be concerned about the racking forces it would put on the spreader ends which could break.

It'll look very similar to this bench and I'm considering adding the dowel to screw through like Jon did.

I'll make a test piece, but would love some input before I go through the trouble. Thank you!

You might consider changing the half-lap joints to this. You dado the sides of the stretcher so that it has shoulders to lean against the upright. This gives a lot more resistance to racking than a screw.
Attachment 516778

I like Jamie's idea of dados over half laps here. Half laps in this case can also lead to some short grain on the end of the stretcher/spreader that extends beyond the leg, making it susceptible to snapping off.

If you did two stretchers in housed dados like in the drawing above and placed them closer to the edges of the legs, that'd be better from a racking perspective. Tight joinery will be important. Also, this depends a lot on the dimensions of the piece and it's intended use. A short-ish bench mostly used to display small items? Do whatever you want. A long bench that will live outside or in a mud room where three large adults will all regularly plop down together and swing around putting on boots, etc.? You'll need to up the strength.