It's bunk

Never heard of them, that fact they require full payment upfront speaks
volumes, Alex

Lots of people have inquired, over the years.
Nobody's come back to say that they've been cured or their life's been
extended.
Looks like a lovely place for fresh air, swimming and nutritional advice,
but otherwise, it's a bunch of mumbo-jumbo quackstuff on their web page.
A cruise is probably less expensive and more interesting and would do the
same (fresh air, destressing and nutritional advice).
I'm sure your relatives mean well, but really shouldn't be sending you
quack sites.
Cancer doesn't happen by "soiling". <what a strange thing to put on their
website>.  You can't "clean up" cancer with meditation, art therapy,
sing-a-longs or a psychologist and fruit and vegetables, but you can sure
find that in your local resources.
As Steph told you earlier:
The options are:
1) Go to your oncologist for the chemo
2) Accept that surgery is enough for you, and only consider chemo if/when
the cancer recurs and causes symptoms.
Nobody can make that decision for you - discuss with your oncologist.
J