I can't imagine how bad the air quality is over where you are. We have air quality alerts here in Port Perry Ontario and it's from the smoke coming from your end of the world. You're 3839.4 Km west of me and your smoke has us stuck inside!!
Getting the valve seats cut and valve faces ground should cost you about .3mm on the shims ONLY if the shop doing the work knows that you're bound by the shim allowance and takes off minimal material, So if your shims are now at 2.60mm or larger, you should be fine.
I was in a similar situation and had the valve seats cut. The shop wasn't paying a great deal of attention and cut them too deep. In order to make up some shim allowance, I ordered new valves. Strangely, the new valves only bought me .1mm in shim thickness so the only "Fix" was to start replacing the valve seats in the head and when I get the machine shop to cut the new seat faces, I'll instruct them to cut them so I start at 2.80-2.90 mm shims. That way I'll be able to reface several times before seat replacement.
I think Kawasaki machined the new heads at the factory to fit 2.50mm shims and left us with nothing for a machine shop valve job. Makes me mad to think that they probably did this intentionally.