This is shocking.
Someone needs to call Animal Control on these Grandparents but seriously, LC, I don't know how old you are, but you cannot tell me for ONE MINUTE that you think what they are doing is right and I know you don't because you've said how wrong it is.
NOW, take the high road and give these rabbits a new home with someone who can be more responsible for them.
Own it and move on.
You obviously know for a fact that this is not a suitable enviroment for these animals.
Even if YOU are the most responsible pet owner on the planet, if you live with adults who are not cooperative and who are abusive and neglectful nothing you do for them is going to keep them safe in their cages. You said it hun, your Poppy would take the hinges off the cage or tear it apart. THIS IS WRONG.
You are also not around enough it seems. If you are going with your Dad for 5 days and these are your animals, then they should be going with you or you shouldn't have them at all.
Please, list them on Craigslist, or make a flier for them and find them new homes with people who will take care of them properly.
When you are older and not living with these people anymore then you can try having rabbits again but it is NOT fair of you to put defensless animals like rabbits in a living situation where they can be tossed from their homes at any moment.
To continue to keep them and allow them to live like this is really not good for your character as an animal lover and is simply selfish.