My daughter was not dx'ed until she was 7.5. She was not well at all by that time, but obviously after all the waiting and worrying we'd already done for several years, a week or two in one direction or the other would not really change anything. However- let me tell you- once we'd seen the dr that ordered the sweat test, I was SO grateful that it was going to be the coming Monday morning (only 4 days away) and not weeks away. Once you've reached that point where some kind of answer may be within your grasp (though I must say I knew almost nothing about cf at that time), you just.want.to.know.
However- I am glad you have it set up the way you do- the sweat test and then seeing the drs in person right away, esp should the results be positive. We got our results via phone call later that day. Now- calling and telling me to come in would not have been practical (we live well over an hour away) and I would have known something was 'wrong' if they refused to tell me over the phone, so the dr calling me herself the way they did was merciful- but it was HARD, hearing that at home, and then waiting a couple days to go in for our big CF 101 Appt etc.
Much lower odds of allergies causing the nasal polyps is a bit concerning and increases the importance of getting this workup done.