Speaking as both a former DBA manager and former DBA - major financial institution with 2500+ SQL Server boxes from dinky little databases of 10Mb to multi-instance cross-site clusters databases in the hundreds of terabytes (not to mention Oracle/Sybase/IMS/DB2) - your role is not to be a DBA, but to construct the framework to enable your people to do their jobs, and to get what they need to deliver. Not to be a DBA. If you try to be a better DBA than your staff, you will fail as a manager. Instead, you will want to micromanage them to death, and they will not respect or trust you, and will resent your very existence.

The most important lesson I ever learnt as a DBA manager was when to let go - even if you know the answer and your DBAs don't, you have to step out of the way. Of course, that never stops you from offering some gentle hints to keep them moving in approximately the right direction - but let your DBAs own the solution. Even if it means they make mistakes.