Are there any risks to granting users SQL Server SHOWPLAN permission?
Take a look at Showplan Security in Books Online, which says:


  Users who have SHOWPLAN, ALTER TRACE, or VIEW SERVER STATE permission
  can view queries that are captured in Showplan output. These queries
  may contain sensitive information such as passwords. Therefore, we
  recommend that you only grant these permissions to users who are
  authorized to view sensitive information, such as members of the
  db_owner fixed database role, or members of the sysadmin fixed server
  role. We also recommend that you only save Showplan files or trace
  files that contain Showplan-related events to a location that uses the
  NTFS file system, and that you restrict access to users who are
  authorized to view sensitive information. 
  
  For example, consider the following query:

SELECT COUNT(*)  FROM table_1  WHERE column_1 &lt; 10 

  
  If a malicious user produces Showplan output for a set of queries like
  this example, and replaces the value "10" in the predicate with
  different constants each time, the user could infer an approximate
  data distribution of the column values for column_1 in table_1 by
  reading the estimated row counts.


This risk does seem negligible, especially given this is a development server, where all queries would be from devs and IT people, not users.