Do you want callers to be able to dial 2-digit extension numbers directly? ("If you know your party's extension number, you may dial it at any time"). If so, consider that your extension numbers start with 10 and go up to some maximum, probably in the 10's or 20's, depending on how many phones you have. So, you can't have callers press 1 for some function and also dial extension numbers that start with a 1, the system won't wait to see if they dial anything more after the initial digit.
However, I've seen most churches want calls to filter through the office, and not allow callers to dial extensions, like the Father, directly, so you may want to set it up to NOT allow callers to dial 2-digit extension numbers directly.
Since there were 5 release of Partner Mail VS, the features available differ. In general, create a mailbox that is not associated with a particular telephone, record your mass times as the outgoing message, and in the Automated Attendant, make Selector Code transfer to that extension. The mailbox will answer, the caller will hear the mass times, and be prepared to have people leave messages and get mad that no one checked them and called them back!
Make Selector Cose 2 transfer to your Office extension. If you need more than one phone to ring when the caller selects the office, you need to put the office extensions into one of the 4 calling groups, and then make Selector Code 2 transfer to that group.
To find out which release your VS mail is, log into the System Administrator's mailbox, (99), and just listen to the full announcement, which will be something like "Partner Mail VS, Release 5"
Post more detailed information, and detailed steps can be given