The MC server occasionally just shuts off for no reason, and Oscar has to restart it manually most of the time. Even if it says it is offline, try to connect, because I have seen it say that there is connection issue even when no issue exists, and the server loads just fine.
Yes, especially when the Lego bricks aren't even cubes. So you go to a bit of effort to make your lego model look like a minecraft set, which is stupid. The pieces they provide are also tiny, so not even suitable for younger kids.
Maybe but everyone spends way too much time staring at a PC screen really - so if you can coax kids away to do something away from the PC probably a good thing in my opinion!