Getting error on Kids Amazon Kindles when opening Minecraft on their profiles

Minecraft was working fine until it wasn't...now I am running into multiple issues, and am not a novice to this.  I purchased Minecraft on my Amazon Kindle for my eldest son to play.  And then later his two siblings wanted to play also.  I allowed Minecraft on their profiles and things seemed to be fine after.

I am now running into multiple problems.

• The two siblings can only play when their brother is actively playing.  Why are they unable to play on their own?
• I now get a 'Pufferfish' error when the two youngest want to get on Minecraft.  I went into the profiles and allowed storage etc and still have this problem.  They can now only play Minecraft on the parent profile.

I would like to have ONE email account that has the three kids profiles - is this possible?  Or do I need to buy Minecraft three times and create their own profiles with three different emails??  

Please help.  Thank you!

One Confused Mom