[xubuntu-users] Off topic, suggestions for light weight linux OS

[Art]

I need some help deciding which linux distro to install. It's a special
project which needs the following:

Must run directly from a usb or sd card
Must support gpg for strong encryption (gpg)
Must be light weight and fast loading*
Must offer an encrypted home folder option
Must store unencrypted files securely if needed, can't be a 'live' usb/sd**
Must load FAST
Must support wireless
Must be secure, high security is a plus
Prefer xfce, not mandatory
Prefer long life cycle, such as Ubuntu's LTS
Prefer no frills
Prefer Xubuntu, since it's what I use***

*only needs to do firefox, thunderbird and an IRC client (non browser type)
**unless persistence is enabeled
***I'm not sure Xubuntu can be made light weight enough to load fast

This is for family and friends to keep in touch and to store sensitive
information on and to send encrypted emails. In a nutshell, the family
members that used to call me 'paranoid' because I used linux have seen
the light. Two of them have been compromised and have demonstrated that
they want to have secure installs (by their actions, not just their
words) for comms with family and friends. One family member had a high
security employer maintained computer that was heavily bogged down with
firewalls and antivirus software! The special linux installs WILL NOT be
their primary computers (for the time being), so the linux installs will
be basically 'single' purpose.

Any suggestions??

TY.