Help with building up a cake please

well My daughter is turning three and I'm going to tackle fondant for her cake. I'm a moron you see... I throw myself into the deep end immediately instead of starting small. I did do one simple round cake with fondant for the first time a few months back. I made the mistake of deciding to do it all in one go. Bake my cake from scratch, layer the cake or "tort" it, whatever, And Make and use marshmallow fondant for the first time. It wasn't a total disaster... It was a bit wonky and the fondant was so thick nobody could eat it all haha. But not bad for a first try.

Now... The cake I'm going to create is a Larry Boy cake. He is a superhero cuecumber from the children's cartoon called veggietales. Google is your friend if you don't know who he is. My daughter LOVES him. I've looked up inspiration on how to make him and decided what I want to do. I'm all set for the eyes, I'm using LCMs to make them bulge. (I think in other countries LCMs go by another name but it's this sticky ricebubble treat you can manipulate the shape of pretty easily) anyways two questions.

1. What do you think I should use for his plunger ears? I've never used gum paste. I was considering trying to make the plungers out of fondant and leave out to dry out???

2. My main question, I want Larry to be 3D-ish not just flat. But how would I go about building him up without leaving a crumby uneven mess?? I know a decent crumb coat will help with some mess but still, the less bad shape the better :-)
How do i build up the cake so that the fondant still looks smooth not bumpy and lumpy?

Thanks so much!