Wooden guest book pen ideas?

knottie655a9ec81e57aed1

I bought a wood guest book shaped like a castle. My guests are gonna write their names on a wooden heart and drop it in. What types of pens/markers would people recommend? I would prefer an array of colors. I’m just afraid they will bleed when writing 

MobKaz

I think to avoid bleeding, you will need to use paint markers.

Jen4948

Make sure that the castle and the hearts are free of splinters.