Noons,
I looked long and hard at websites for hosting for the same reason you want to (wider family access). I had 20 years of research (although fewer than 700 individuals) and finally settled on tribalpages about 4 years ago. Primary reason was that I could easily limit access to people I wanted to have access.
TP offers a free site, and I used that for almost 2 years. I finally upgraded to an inexpensive paid site when I wanted to add more photographs and more detailed stories about ancestors than the free space allowed. Your wish that family members "could add to it" (the site) is something that TP allows, but not something that I would ever do. I have seen too many people who are willing to accept anything they hear or read as gospel, and I only permit well-researched data in my tree.
Also, with TP, if you don't pay for a year ($25-30) the tree isn't "lost". It simply reverts to being a free site with certain size limitations imposed. On the downside, since it a small operation (unlike so many) they don't have on-call technical support for every little problem, and rely on other forum members to help resolve an individual's problems. I have noticed that most of those problems come from people who are novice computer users who aren't really comfortable with the technology.
Here is a link to the homepage:
http://tribalpages.com/ Nick