The value of a spoke is greatly under stated, and the cost is over stated. Nothing wrong with 24/28. Won't weigh much more, won't be much less aerodynamic. Will be much more bombproof though. While 20/24 would be "sufficient," you stated "bombproof" as a requirement. At your weight, 24/28 is the bottom end of what will be bombproof, assuming you wish to ride these wheels until the braking surfaces wear out, and never have to take a spoke wrench to them.

The build quality has a lot to do with this as well though. Make sure tension is even and adequate, and the wheel is properly stress relieved.

Since I saw it up there, don't do a 28/28. Wasted spokes up front.