Counting Smarties concentrates the mind wonderfully. Particularly if you allow the child to eat the subtracted ones.
Seriously, though, I am not at all negative about teaching children to be comfortable with maths or about teaching them maths. I did a heavily science based subject which required a lot of higher level maths for my first degree and my mother was a maths teacher for many years and taught in some fairly challenging environments, including a couple of borstals. She was a good teacher and I think she taught me to be one too, in the small home-based arena where I have the opportunity to practice that skill. However, arithmetic is not maths (although it is valuable in its own right) and rote learning number facts is not maths (although it may be useful for a small subset of children).
It's a bit like phonics, actually, a subject close to the Primary Education topic's heart. Either you can give the children tools to enable them to discover words on their own or you can encourage them to learn whole words one by one and remember them. If you're quite bright or maybe just reasonably interested, you'll probably work out the phonics code alone from the latter type of teaching, but many children will just keep remembering the facts they have learnt. Kumon is a bit like whole word recognition. It's practice and recall and doing it as quickly as you can. It's not without value, as those skills are useful, just as it's useful to be able to look at a word and read it without looking at its component parts. But it's not the whole story and actually I think that it isn't developing the maths part of the brain as well as doing something maths based that isn't so restrictive. I also think that possibly focusing on those recall elements of maths is directing the child's learning along a path that is ultimately not very helpful to the things that come later and which require more than remembering things. Having said that, some instant recall of eg number bonds is helpful just to speed up your mathematical life.
I see that you say that your daughter wasn't engaged with counting apples and raisins. Maybe she's just not ready for it. If she likes the worksheets and completing them more than she likes counting and adding and subtracting and dividing raisins, then IMHO you are encouraging her to like the reward of getting it right better than the reward of finding something out and I think that is a shame, particularly for a child who isn't even at school yet. You say she's bright and perhaps it won't matter to her - maybe she will just work out the code alone. But it's a missed opportunity in my view. And possibly she will bypass the finding things out stage, be great at arithmetic but not really get the ideas behind it which will be far more valuable to her later on than any amount of good mental maths. I am saying this, btw, as someone who is good at maths and did a lot of it at university and yet is still rather shaky on arithmetic. It honestly made very little difference to me. Interestingly, my mother's good grounding in real maths meant that as things got harder, I got better at them. I would rather by far that my child was good at GCSE or later maths
As you say, it needn't take long, but I think counting leaves in the park for ten minutes is hundreds of times more valuable than counting leaves on a sheet of paper.