Ok.. before I even start, I am sure I know what most the the answers will be, but.. here goes.

I have two very good customers (they are sisters-in-law) who are having a joint graduation party. J's daughter graduated college and wants a Vanilla cake with chocolate pudding and fresh bananas with buttercream, decorated in green and gold.

A's son is graduating from 8th grade. A wants Vanilla cake with vanilla pudding and raspberries and ganache frosting, decorated with purple and gold.

This party is for 125 people. I told A, that 1. it is difficult for me, with my kitchen space being very small, to do a LARGE cake with ganache frosting. (We are talking sheet type cakes not tiers.) 2. It would make things somewhat nutsy at the party, when people started asking for one cake or the other, or quite possibly a piece of both.
I suggested that she consider doing a buttercream frosting so that both cakes would look a little nicer on display. (just my HO)
Needless to say, A is not thrilled with this idea. I am toying with the idea of doing two medium sized sheetcakes with the buttercream, and a two tier cake in the ganache. This could be displayed with a sheet cake on either side, and I think the respective color schemes would look better. The ganache cake could be decorated with white, or just the gold.
Just for additional info, A's guest list is larger than J's.
Any opinions?

What about one big sheet cake for the party and a couple of 6" rounds, one for each graduate, in the colors/flavors of their choice?

I agree ...
Maybe one vanilla and one choco sheet cake (most everyone likes either flavor) and then the 6" rounds for the guests of honor in their flavor choice.

Is this a paying gig or just a favor? If you are being paid I'd give my opinion and then do as I'm told.. but I'm volunteering my services I'd take their requests and them tell them what they are going to get.

Debi, I think your idea is a good one.

Call me crazy, but shouldn't the college grad's cake be a little more distinctive/bigger, something, than the one for an 8th grade graduation? It is obviously a major accomplishment!

I don't even know if this is possible to do, if yes how difficult. I am totally new to this. Here is what my thought.

Make the center as per J. (A square or an oblong cake) and make couple of sheet cakes as per A and cut them into strips and put them around the center J's cake. If you are making the center in gold and butter cream and make the surrounding in raspberry and ganache, that itself makes a beautiful design and you should be able to take care of both of their needs.

Please don't laugh at this idea though.

Well, I must admit, thecreativeone4 has a valid point. Yes, I am being paid to do these cakes, so I will go ahead and do exactly as each customer has asked.
I must learn to keep my 2cents in my pocket (so to speak).
If they have issues with the two different kinds of cakes at the event, it is their problem, not mine.
I do appreciate you all taking the time to give me good advice.

Thanks