if you’re kegging the beers and are going to keep the keg cold for the entire time, you can probably just sweeten the beer without pasteurizing or sorbating, the residual yeast in the beer is probably not going to be very active at fridge temps (though I have had some wild yeasts keep on fermenting stuff in the fridge).

Alternatively you can also mash hotter to produce a wort with fewer fermentable sugars which will result in a sweeter finished beer, you can also reduce the bitterness of your hopping to swing the balance of the beer flavor towards the sweeter side of things.

I’d try all of that before attempting to low temp pasteurize your beer.