I would like to use bettercreme on a childs birthday cake and was wondering if fondant decor will hold up on it?

It really depends on the extent of the decorations. If you are just going to lay some decorations on the top of the cake. If you do that at the last minute it would be okay. I don't think the whipped icing would hold decorations on the side of the cake.

Yes you can use it. The three tiered blue cake in my photos was frosted in Frostin Pride which is the same thing as Bettercreme. I have a fondant band around the bottom and fondant stars. Cake sat for four hours before serving and fondant help up just fine.