a few questions on Espionage 3 and FileVault 2

I have been using Espionage 2 for a while and now also have Espionage 3, both work fine with occasional hiccups, nothing drastic so far.
The Espionage 3 announcement recommended using FileVault 2 for encrypting application data. But in my case I have 4 users on one Mac, and only one user has something worth encrypting, while two other users are kids and I don't want them entering passwords or being involved in encryption in any way. So my questions are:
1) will FileVault 2 work for this multi user arrangement described above?
2) if yes to 1, will there be a performance penalty?
3) if yes to 1 and no to 2, why use Espionage at all rather than just FileVault?
4) can I run both Espionage 2 and 3 at the same time, 2 for applications and 3 for other data? So far it seems to work OK
5) the update to Espionage 3 promised to allow Library folder encryption, and I don't mind manually unlocking those folders - are there any other reasons not to use Espionage 3 for application encryption and ditch Espionage 2?
The Espionage 3 announcement recommended using FileVault 2 for encrypting application data. But in my case I have 4 users on one Mac, and only one user has something worth encrypting, while two other users are kids and I don't want them entering passwords or being involved in encryption in any way. So my questions are:
1) will FileVault 2 work for this multi user arrangement described above?
2) if yes to 1, will there be a performance penalty?
3) if yes to 1 and no to 2, why use Espionage at all rather than just FileVault?
4) can I run both Espionage 2 and 3 at the same time, 2 for applications and 3 for other data? So far it seems to work OK
5) the update to Espionage 3 promised to allow Library folder encryption, and I don't mind manually unlocking those folders - are there any other reasons not to use Espionage 3 for application encryption and ditch Espionage 2?