SO I am making a tiered cake with the glass beaded numbers 30 as the topper..
I would like to illuminate these numbers as we will be in a dimly lit bar.
Has anyone ever tried this.........

I want to sink those battery operated tea candles into the cake si they sit just below the surface on the top tier , hoping this would direct all the light upwards as opposed to if I just let the set on the top of the cake.

What do you think?

I put a candle into the cake. I hollowed out a spot the size of the candle/tealight, lined it with wax paper and didn't have any problem. It wasn't very heavy though. Check out in my photos.

I don't see why the battery opperated tea candles wouldn't work! Just do like you said, sink then into the cake, I would decorate around them to tie them into the cake decor. It should work out great, I love the idea!!

Post pics so we can see it!!
Go for it!