HelloCustomer- Thank you for using Just Answer.
I make cakes for a living so I can definitely help you out here!
If your cake has a fruit filling, you MUST refrigerate it until the day of the wedding and take it out at the last minute whether you use butter cream or marshmallow fondant. You can transport it and then put it back in the refrigerator or at least in a cool area. Butter cream is less forgiving in the heat than the marshmallow fondant, but they are both subject to being destroyed by heat. Do not place them outside or in the sun as they will melt!
Here is what I do: I bake my cakes on Monday or Tuesday for a Saturday wedding.
After they have cooled, I wrap them in paper towels and press and seal or saran wrap and leave them on the counter overnight to settle. Then I put them in the refrigerator until I am ready to fill them and ice them which is on Friday. If there is no filling, you can decorate them and leave them on the counter until the wedding as long as the area is cool. I would cover them if there are pets around so you don't get any hair or foreign objects in the icing, but once butter cream and marshmallow fondant "crust", they are good to go on the counter until Saturday. Good Luck and thank you for using Just Answer!
P.S. You can freeze the baked, unfilled, un-iced cakes for up to 3 months, but they have to be covered with saran wrap and aluminum foil and placed in air tight containers while in the freezer and then you have to let them defrost for at least 24 hours on the counter before you can do much with them. Renee