Really good answers above...
.. but also & pointedly....
I would ask someone starting out to look very closely at logistics & weak links in their "preparedness philosophy".
Like....if things got really bad...
How quick could they relocate their ammo stores??
What is the maximum amount they could relocate if using every member of their party??
How quickly could they load stored ammo into magazines??
Do you have a means to allow non-shooters to quickly replenish ammo into magazines??
As it doesn't matter if you have thousands or 10's of thousands of rounds per gun..
..if you cannot replenish magazines quickly enough to defeat the threats!
Questions like these can be answered here....
Also you might look at optics (Aimpoint, EOTech, etc) for your long guns that allow quicker, more effective targeting on moving targets..
..especially during low light & night time hours.
Night Vision is value added here!
You can waste a lot of ammo if you cannot see what is assaulting you & yours!
Striving to make each round of your ammo count....
..is what counts!
As far as what additional weapons (or add ons) you might add..
That really depends on your budget & how far you want to go..
I would have a inexpensive, reliable, compact, semi-auto pistol with holster & extra mag for every secondary member you expect to have in your group....standardized...something like a Makarov (I have CZ-82 loaners)
Also a training gun for each of the younger members..
..this setup was my daughter's 10th birthday present.
...which led to this Saiga for her 13th birthday present,,
Longer range DMRs for adults in the group...