After SHTF it’s not time to plan, it’s time to put the plans you have into practice. Starting with assessing the current situation, taking inventory of your stored and stockpiled supplies and then determining what members of your community are available and what their needs are (because they probably have not prepared anywhere near the level you have.
When SHTF first hits and everyone is scrambling to feed themselves and to simply survive, you won’t see many people out wandering around I’m afraid. You will need to wait a while and allow all of the stupid people to die off and food production to be reestablished before any real communities can even be formed. During this time you will be in survival mode and trying to keep a low profile if you can. Getting together with the neighbors will probably not be real high on your list unless you are being constantly attacked and need the backup. Now maybe it’s just me, but I don’t consider the two neighbors on each a side of you to constitute a real community, even if you do live close together. No, I’m talking about the ones that are spread out in whatever local town may exist. If there are any that survived that is.
So let’s say you have a nice little group at your homestead and are doing just fine by yourselves, why would you need to bring others into the mix? The simple answer to that is that no matter how well you prepared, you are bound to overlook things that you will inevitably need to survive. You will also need the talents of those that live around you, such as medical and veterinary services that you may not have. You will also need others to barter any excess food or supplies that you may acquire and need to trade before they go bad. Other items that you may want to barter with or for would be items like fruit trees or honey. (Sugar will quickly become in short supply.) Thus the need for a trading post and the exchange of information as well as human activity from time to time. Children will not stay small forever and will need prospective mates when they grow up. No, staying hidden away after SHTF would not be to your advantage.