visiting usa every 3 months under visa waiver

i just want to clarify.

over the past 4 years ive visited usa a total of 9 times, ive always returned to uk when i specified, shortest trip was 5 days, longest was a month.

I have family there (sister) and my long term plan is to move there using a sibling visa, im not planning on doing this for at least the next 6 years when my son will be old enough to decide if he comes with me or stays in the uk, but in the mean time, i want to do 3 months a year over there, 3months here and a month there ETC.

I just dont want to get into a situation where i have problems with immigration, they always make me feel guilty when im entering as it is. my understanding is that i can spend 3 months a year in the usa under the visa waiver programme? Im just wondering if theres proof i can always carry to show I have every intention to return to uk each time. I own my own property here in uk, my own ltd company of which im a director. Would taking proof of this be a good idea? If i was ever to get refused entry it would mess up my long term plans so this is very important to me.
thank you