How to convert SQL 2008 shared disk cluster to SQL 2012 non-shared disk cluster?

Hi experts,

  I am going to convert SQL 2008 cluster to SQL 2012 AlwaysOn. I want to do it easily and minimum downtime/risk.

The first one is:

1. Uninstall SQL 2008 cluster
2. Install SQL 2012 standalone on node one and node two separately(default instance)
3. Add listener(virtual host)
4. Re-attach db
5. Start (SAP) application

Downtime(item 2, 3 & 4) is about 1 hour

The second one is:

1. Install SQL 2012 standalone on node one and node two separately(named instance)
2. Add listen(new virtual host)
3. Re-attach db
4. Copy login account from SQL 2008 to SQL 2012
5. Reassign (SAP) application to new virtual host

Downtime(item 2, 3 & 4) is about 30 minutes and more importantly, rollback can be done immediately