Jeannie,
As I recall (I don't have Project open at the moment), the Resource
Names field uses comma delimiters between each Resource Name.
Unfortunately, Project will only wrap text based on the presence of
spaces in the text string.
However, in my opinion, ten (10) resources on a task seems a bit much,
in fact, excessive. It sounds like the task is to general. You would be
better off breaking the task into smaller functional or organizational
parts so that fewer resources work on each part. It will be much easier
to manage and track progress. Be careful however to provide a logical
linkage between each of the smaller task parts.
Hope this helps.
John