My daughter is insistant that she have cupcakes at her wedding...300 of them. Each one of them will have some type of decoration (flower, butterfly, mushroom, etc...) on top. She want's all the decoations to be edible, so no gumpaste. If I use fondant, how do I store them to keep them fresh, and how far in advance can I make them? Would I be better off using modeling chocolate instead? Any help would be greatly appreciated.

They should be stored in an air tight container, such as ziplock storage containers. I line the bottom od mine with wax paper, put the decorations in then fold the wax paper over them, and seal. Then store in a nice cool place out of direct light. I also let mine sit until they are dry before storing....no moisture. Hope this helps. They can be made up to several weeks in advance...Good luck!!!

I personally would use modelling chocolate.

Store them in single layers; some if flat can be stacked in layers seperated by wax paper. Put them in air-tight/sealed containers and fz. That means you can start now Unless you want total look-alike items, I would vary the use of fondant & modeling choco.
Try making say 3-4 of each and fz them for a week, then take them out to see how they are doing & make sure they are holding up & defrost o.k.
Once on the cupcakes do not put them in the frig! There are several posts on this site where people have and the decoration melted

They can be put in a container and frozen.

THANK YOU ALL VERY MUCH. The wedding is in May, so I was hoping to get started on them by February. In the menatime I have some left over fondant and chocolate that I wil use to "test" freeze them and see how they turn out.

Just know that you have about a minute after taking out of the freezer before they become sticky. You can let them come to room temperature and they will dry out a little.

I would use chocolate too but the chocolate molds (cheap $2) that you can fill and freeze and then store.