This is the first time im doing this which is why im asking....I will be making cakes and plan on covering the cakes in MMF. The cakes will be delivered on Dec. 26th. How long in advance can i make the cakes? When would i be able to apply the MMF and finish decorating the cakes?

Is someone paying you for this?

um... it depends on how long it's gonna take you to cover an decorate them. which be depend on how big these cakes are. is it a tiered cake? how many tiers?

Well you could bake in advance the freeze to save yourself some time. There are lots of threads on it on here about it.
I have covered in fondant 2 days before (so for you the 24th) in the evening and then finished decorating the next day (Christmas) for the 26th. But if there isn't a lot of decorating work and the caek isn't needed till later in the day maybe you could cover on Christmas and decorate the 26th in the morning. If you have never done this before (i'm not really sure if you mean never done a cake like this,or at all, or if you have just never made cake on a holday) then I would give youself lots of time for error and have plenty of extra supplied on hand since the stored will be closed for you to get more.

The Mat by sweetwise would be a good investment and will make applying fondant much easier.

It certainly would help us to have more details. As has already been asked:
what size/kind of cake(s) & style being used are especially important to know.
Yes, lots of things can be done ahead like the baking (wrap well & fz); make the b'cream/fondant - keep in frig; depending on what decorations being used some, if not all can be made now too.
All of that would mean doing the actual decorating work can all be done on the 23rd or 24th.
Good luck and let us know how it goes

MariaCakestoo=No, im not getting paid for this...the cakes are gifts from me to my cousin for his grad party!

For the rest of you...thank you all for responding so quickly

The cakes that I will be making will be squared cakes. It will be 2 "tiers". One will be a 9x13 and the other haven't decided yet, either a size up or a size down. Basically what I will be doing is stacking books. (yes i will use douls in between) I will bake, crumb coat then freeze/refrigerate and lastly cover in MMF and decorate.

**to make the MMF in color, do i mix in the color while the marshmellows are melting or after the whole mix is complete??**
Hope this all helps and again THANK YOU to all who responded and for your help!

You may want to practice covering a square cake in fondant.. its a little trickier than covering a round cake.. just a suggestion.

Since you have time, you could get Sharon Zambito's DVD on stacked book cakes. Her DVD's are the best and reasonably prices.

You can color fondant either while making (I do this if I want the entire batch to be one color), or after it's made. Some colors are harder to achieve than others (namely red & black). I've had good luck making those richer colors with candy melts as opposed to gel/paste colors. Here's the link to he instructions:

http://sugarsweetcakesandtreats.blogspot.com/2010/11/recipe-red-marshmallow-fondant-mmf.html

HTH!