SQL Server Security

I have been put in the awkward position of needing to publish our internal SQL Server to the web for a particular client. I also have to provide them with a user name and password to be able to access the database through a software application. They need to be able to execute SP’s and do select, insert and update on tables. However I want to restrict them from viewing the database design through Enterprise Manager or similar.
I have restricted their access so they cannot make changes to the database but they can still see the table and SP design which I don’t want them to see.