I will be making a 2 tiered red velvet cake with cream cheese frosting covered in mmf. I will be making the cake topper out of RKT and covering that in mmf as well with icing images used for the decals. My question is  how soon can I start making the cake? would tuesday night be to far out if i was frosting the cake on wed covering in fondant thursday and doing final touches friday?! Also what is the soonest I can make the cake topper?

I am a hobby baker with a full time job, and always need to plan ahead.  I would make the cakes anytime within a few weeks ahead and freeze.  Frostings and fillings can be made several days ahead of time at least and refrigerated or frozen.  RKT can be made ahead of time, and last for a long time well wrapped. Fondant and gum paste decorations can be made in advance.   Beginning early the day before I defrost, fill, frost/fondant, and decorate, sometimes finishing the morning of if not due too early.    I don't like to have cakes out  more than 48 hours if possible, and less than that once filled, depending on the filling.  I wouldn't leave cream cheese frosting unrefrigerated for more than a few hours.  I have not used fondant over cream cheese frosting, but I have read a few discussions about problems with that combo and have avoided it.  To have the cake out 5 days out seems a little too long to me, but again that is just an impression, I have not tried it.  Good luck!

I probably should mention the cake will be refrigerated during the entire process as it is ok to refrigerate mmf. I would never leave a cake out for 5 days. The last cake I made I did within 2days but I felt it was rushed. I think i might fill the cake with cream cheese frosting and cover the outside with butter cream as to not have issues with the fondant!

Freeze, don't refrigerate.  And make the topper right now.  Andcrazy4's advice about the cc and bc frostings is spot on.