Fact is, if the lawn is a cool-season grass like fescue, it isn't going to grow as quickly in 100+ temps as it is in April, no matter how good a job of irrigating is being done. Don't make a big deal of it. Skip and see how it works out next week. I'm guessing it won't be as difficult to mow as you think.
Ultimately, the customer has the final say. We can posture all we want to, but to me, it often isn't worth it. I had an elderly customer who insisted on going bi-weekly early this spring. Nice home, affluent neighborhood, lush lawn that had obviously been fertilized prior to his buying it last fall. I told him it wouldn't work, and convinced him to stay on a weekly schedule until growth started slowing. The next week I show up to mow, and he stops me, saying he wants to go to EOW. Two days shy of two weeks, he calls me up saying his lawn looks like it needs baled. I told him it would be two days, or perhaps 3 (regular day to cut) before I could get to it, per his instructions to go to EOW. He asked if he should just get someone else, I told him yes, and that was it.
Today, I mowed a property that I would not have mowed if it had been strictly my decision. Place is on a hill, thin soil, limestone actually protruding from the ground in several places. Dries out more quickly than any other account I have. Normally, we mow it EOW, but it had been a full month, and the owner, a retired Air Force colonel emailed and said he couldn't stand looking at it any more, even if it was too dry, mow it anyway. I was cutting off, at the maximum, maybe 1/2 inch of growth, and a longer weed maybe maybe sticking up in every 500 square foot lf lawn or so.
Dependable Mowing Service