I am a hobby baker and make cakes just for fun. So I still have a lot to learn. There is a friend of mine who wants me to make her son a dinosaur fondant cake (whimsical) and the inside would be rainbow.....just like the one I have under my pictures. Anyway........I was thinking it would be super fun to have a hollow removable volcano on the top. I was wondering if I put a small cup/bowl of water under the volcano w/ a piece of dry ice and some water if that would make the volcano "smoke". I'm also wondering if it's going to cause the water to bubble and splash all over the fondant. Any tips would be greatly appreciated, thank you!!

Wouldnt the dry ice on its own, ie without the water, smoke?
An eggcup/shot glass might be enough instead of the bowl.

When is the cake for or could you try out some options beforehand to see what works best?
Coloured boiling water with ice cubes dropped in will create steam but it depends on the age of the children if you would want to have boiling water near them.

If there is a danger of having the volcano water spill onto the cake you could put something on top of the cake to allow the water pour away down the sides without causing damage to the actual cake. Alternatively you could use marshmallow fluff instead of water and allow the volcano to erupt down the cake and then just eat fluff and all (if you google it some people have done it before so you could get directions)

Ive done a smoking volcano cake. I made a hollow section at the top and put a plastic cup (glass can crack with the extreme temps and metal sings when dry ice hits it). Then I put a couple of pieces of dry ice a few drops of water. Go easy on the water and you won't have any bubbling over issues. I used buttercream and had no problems.

I used buttercream on one with no problems as well and you will need to add a bit of water to make it smoke