I would just do a round cake and carve out that little piece on the right side to make it a "C". Like 1" into the cake. Then to make the C and S, I would just do some layers of frosting or fondant to make them look 3D. Like it shows in the pic. You can make a slightly larger cake board and write their anniversary in frosting on the paper!
Good luck with Ideas! 
I also think a round cake with a transfer would look nice 
How about if you bake a regular round + an additional tier to completely carve the large C with the S in the center. Perhaps you can make a plaque out of gumpaste to complete the logo portion of cee-san. Hmmm
that's what i instantly thought of too...gives it alot of dimension, and you could always use the scraps for cake truffles.
what about the cinco de mayo concept? I think you should throw in some mexican theme.
I will try and incorporate that too.
I have another idea. Would this work better? Kind of a version of topsy turvy, with sheet and the logo sunk in cake at angle?
That's clearer Jilbry.
I think you can do this to stand up on a sheet cake by baking a deep deep round tier... say 4".
The logo can be applied to it in any number of ways and then stand the
tier on on it's side dowling it to the sheet cake.
Edited to say, I see you have another possible look, and I think that might be easier than a full round.
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