So it turns out Multiplayer can be both good and bad. I invited my older sis to one of my servers today shortly after lunch to show her around one of my giant "base" networks.
As it was, my sister likes to build in Minecraft, and only that. She has close to no experience mining, and even less fighting. To top it all off, she always plays in Creative. However, my server was Survival, but it was in Peaceful mode.
We explored a lot of caves, hung around one of my houses, and I learned that:
Pros of having people behind your back
1) Someone is out there looking out for you
2) Two people are better against mobs than one
3) I can use commands to troll my sister (/tp PlayerName x y z), where y=256
1) Someone is out there looking for you possibly ready to kill you (my sister and I teamed up, so no PvP- besides, she sucks at fighting)
3) Someone else takes all those diamonds :(
But she adapted well. I handed her a pickaxe, and soon she could mine, too.
We mined a lot, enough to give my sis a full iron set (which actually isn't that much). I found my original jungle base where I had first spawned in the world. My sister got stuck in my pigpen, but oh well. That's what /tp is for.
As a side note, I could have done all of the things I listed in the Con list do my sister. She wouldn't have a chance- I was the server owner.
PS: Don't worry, I still do play ED. Just find it a little boring for now.