2 things
1. About cactus farm causing lag
so i don't think you should worry too much about this. Here's why
cactus growth rates were nerfed. So this farm to the sky's limit plus my other cactus farm would lag less than before the patch that nerfed it (1.0.0)
in addition, it will not be loaded/used a lot. I will move the minecarts away to make sure they don't interfere. In addition, when i'm on the other corner of my place, working on my building, the cactus farm will not be loaded (it'll only be loaded when i need to use it).
also, my planned kolkano wall, not completed yet (35%), will require around 1500 cactus! there, a reason
2. so i herd you were talking about "randome people from the minecraft forum" joining
as long as my stuff stays intact and my unlocked chests stay..."full of items"; i'm fine.