Hi all! Need help.  Mental meltdown, can't come up with a good idea.

My MIL taught preschool for 25 years and just retired, we are doing a party for her, everyone she's ever taught is being invited.  The party will easily be 150-180 people (maybe more?) and will be held at a pretty informal hall.  My SIL came up with the idea very suddenly (our opinion on dates wasn't asked), so I have a fairly short notice to come with the cake and cupcakes to feed that many people. 

My forte is flowers, and originally I was going to do something like this cake that I made for my husband's grandma and grandpa's 65th wedding anniversary a year and a half ago.  My SIL thinks a school house cake would be best since MIL taught preschool.  I don't disagree, but can't come up with a good way to make one.  My idea of making something super elegant (3 tier round cake, 14-10-6, muted colors and perhaps orchids or roses cascading down) seems ... not fitting now that I found out the party will be VERY casual- my SIL is telling people to stop by on the way to soccer game (literally).  Not how I would have planned it, so I am having a hard time coming up with an idea for a cake that would be gorgeous, more on the casual side, but still elegant. 

The numerous preschool cakes I found all seem to center on crayola and apples and teddy bears.  Those are great, not knocking them down, but seem more fitting for actual preschool students, not a retiring teacher? 

The party is next Friday, and in a sensible effort not to overwhelm myself with this thing all in one week (per my usual fashion), I REALLY wanted to have the cupcakes made, the cake tiers baked, filled, sculpted, ganached and frozen this week, so next week I could spend all week (correction: few hours a day I have left between running kids to VBS, swimming lessons, play dates, you get the idea) decorating.    I'm ready to bake, but need to figure out what I'm doing here!

I will also confess to having a Silhouette machine sitting in my basement.  I got it a year ago (*gasp*) and haven't opened it yet.  Have icing sheets (purchased in the same time frame, are they even good anymore?).  NO idea if the learning curve on how to operate the Silhouette is within my time frame, but that's a possibility.  Don't judge me too harshly :)

So, can you PLEASE help me throw some ideas around?

AHow about drawing around each tier and make it look like a child's drawing, I.e. stick figures. I did something very similar several years ago. Sorry, no pictured loaded. HTH!