Unattended install of SQL Server 2008 R2 cluster fails with error - "Illegal characters in path."
Nicholas Cain (@SirSQL on Twitter) published three blogs recently regarding the installation of SQL on a WIndows Failover Cluster using PowerShell to script the activity.

The first of the three blog entries may be found at http://sirsql.net/blog/2011/7/11/creating-a-clustered-sql-install-ini-file-using-powershellpa.html

The second of the three blog entries may be found at http://sirsql.net/blog/2011/7/13/creating-a-clustered-sql-install-ini-file-using-powershellpa.html

Finally, the third blog entry may be found at http://sirsql.net/blog/2011/7/18/creating-a-clustered-sql-install-ini-file-using-powershellpa.html

His approach uses PowerShell and it might give you some ideas.