If I make decorations with fondant, how long will the fondant be good for, and what is the best way to store the decorations?

I plan on making a lego cake made with rice krispie treats and covering them with fondant. I wanted to make these ahead of time so I wanted to know how long they will be good for, and what is the best way to store these. We are going to go on vacation and I want to bring these legos already made to decorate a birthday cake. Any advice or suggestions would be appreciated.

Do you want to eat the RKT with the fondant? Because if you want to eat them, I would say 2-3 days. If you don't want to eat them, you could make them a week in advance. Some things you could make even before that... I mean fondant dummy cakes last years with little people and stuff. I would just be concerned about the RKT under the fondant, which is why I suggested a week. You don't want them to rot or bring in ants or anything else. Hope this helps!

I was thinking of using the premade rice krispie treats. The kind that you fine in the store with the blue box andf blue wrappers. I know that they will stay fresh longer. I am thinking of storing in a tupperware container then. Not sure if they will be eaten or not. I am sure that my kids may want to try them. I would want to make 1-2 weeks before use so the kids may not try them afterall.

Any other suggestions?