You could use a 50/50 mixture or just fondant to make your pins. depending on how big you will make your pins, I would use RKTs only if the pins will be very small because of the weight that rkts hold. And when you add the fondant it makes them heavier.
Sorry, i can't tell exactly what gauge the wires are but, you can get white floral wires from the craft store just be sure to coat (dipped in chocolate and let dry) the area thats going to enter your cake before sticking them in it.
I hope this helps
Also, what type of wire is used to make them pop off the cake?
You don't want them to jiggle on wires, use dowels or skewers.
I just did my first "pop off the cake" decorations. They are the simple fondant balloons on my clown cake in my pics. I glued them on with candy melts & added the curling ribbon...
Anyway - I was pretty happy with using shish-ka-bob skewers. When I inserted them into the cake it felt pretty sturdy. I'm thinking your pins will be heavy though. Maybe do a test with the skewers to see if they work. I think they would hold the pin pretty good. I bought a giant pack for $2. If not...would a thicker dowel work better? (just thinking out loud)
I do like the white wires on the other decorations. I am wondering how the pins stay elevated? I get you can insert skewer or wire on an angle to get different "tilt" but do you dip it in white candy melts and let dry first before inserting in cake?
Neat cake - I hope it turns out good!
Rkt will be lighter the fondant- and less expensive- pack yhem tightly
and then cover- a skewer or dowel should be used to set your pins
I agree- different angles will get you a different look for each pin