Currently what tools (client or web portal) do your users use to access the data? do you have an existing tool?
This is a site dedicated to questions regarding SQL Server and tools.
no tools..only excel...That's why i discussed with Kristen
You can connect Excel direct to the database. There is a login (i.e. a SQL Server login, or Trusted connection) so you can control Permissions to reports.
But the interface (MSQUERY) is dreadful, out of date, and the resulting XLS will be very fragile. Its OK in the hands of very fastidious people who understand the limitations.
Or you could just use SSRS - its SQL Server based, included in the SQL Server license, pretty straightforward to people who use Microsoft products. You can Export to XLS from a report.
But as I said earlier, I have almost no knowledge of suitable / best report writers. If your want some analytical advice to help you decide get a consultant in, we won't solve that on a forum. Here you will get basic information based on the description you provide; that's not the same as a consultant who has looked at your data, spoken to the your people and assessed the skills of the whole team
P.S. We try not to let our users use Excel for data manipulation. Its the root of most of the bad data in our company.
For Ordinary People (non-programmers) the ease with which data is accidentally changed, the ease with which formulae fail to include some cells - when data is moved, or new rows/columns added - causes all sorts of problems. Not to mention the "assumptions" people assume about the data ("I had no idea that figure included Obsolete products" 
)
Any data manually entered into XLS is unvalidated (unlike data entered into a Database Application where "sensibility" of the data can be built into the APP - you can't enter an invalid Customer Code, for example).
So we try to provide whatever functionality that a user might want from Excel IN our APP. This is particularly so when users want "fresh data" in XLS. Typically people make manual changes to XLS to get all the additional "stuff" then need, and then they are loath to refresh the data 'coz they lose all their personal additional data / formulae / calculations. And then they start manually adding the extra, newer, data, or some other ghastly workaround ... and then you have everyone with a different XLS - and that is a nightmare. Or you have someone skilled building the initial template, 5 people then use that, they all modify it to suit their personal needs, all of them with less skill than the first person, and you wind up with absolute and complete rubbish
Ok..Thanks for your valuable feedback and help Kristen