The Sendero and the Sendero II are fantastic incarnations of the 700. Only factory 700 that I would spend money on these days, that and the VSSF II (discontinued now as well).

To your point, a lot of time laying on that rifle is more important than anything else.

Beyond that...

Find a bullet and load it likes, get a proper front rest and bag to shoot from, or get used to a dirty belly.

If it has the X-trigger, tune it down to a comfortable "if I go any lower, it's scary" level for his finger. If it doesn't have an X-trigger, or you can't get there for his finger with the X-trigger, or if this will be a bench rifle with little-to-no hunting time, spend the money, drop a Jewell in it. You can have a trigger job done, but the Jewell will make you happier.

Get a good one piece mount, lap the rings, and saddle a good glass on top of it so he can SEE WHAT HE IS SHOOTING AT over those ranges. The 8-32x56mm Nightforce BR is a fantastic glass for the price, even knowing the price is high. Leupold VX-3 LRT's are a great 'affordable' option.

I hate full length bedding blocks other than to keep the stock stiff. Never seen a Sendero that wasn't properly floated, but I'd still go ahead and throw some glass around it, and make sure it's floating like it should.

But ultimately, with the right load(s), that rifle will shoot better than most guys are capable of achieving, right out of the box.