Hi,
I think your plan will work.
We used to live on Vashon Island. The house water supply was a small creek that originated a couple hundred feet above the house as some springs coming out of a steep bank. This was our water supply, and it also supplied water via a pipe line to several houses below us.
The water from the springs/creek was collected in a concrete tank, and the pipes to the houses came off of the tank.
The county did not like the idea of the water being picked up after it seeped out of the bank because of the potential for contamination, and eventually we drove well points into the bank and piped the output from these to the concrete tank. It does not take very much flow at all to supply a house when the incoming flow to the tank runs 24/7.
We had no trouble with either system -- the water always tested clean.
Our house was about 20 vertical feet below the concrete tank, and we just used gravity feed to supply the house plumbing -- no pumps at all. 20 vertical feet only gives about 9 psi, but as long as you run full diameter pipes right to the point of use, thats plenty of pressure, and it eliminates any need for a pump or pressure tank.
Gary