You probably don't need to use so much that it is squeezed up around the initials. CA is pretty permanant, unless you heat it up, in which case you would destroy your pen as well. The place where these initials go is not going to be subject to that hard of abuse, so there should be no problem with them popping out. If you drop the pen and it does pop out, the repair would be easy, just another small dab of CA, and it's back together.
To give you an example of how strong the bond is with CA glue, there has been some discussion on some of the forums about making small cutting or scraping tools using carbide. The best method for doing this is to get some steel rod and grind a flat in one end. Then buy a carbide insert off of Ebay, and use CA glue to attach the carbide cutter to the steel rod. Then if it ever gets dull, you heat it up, pop off the old insert, then glue on a new one after it cools down. If CA can stand up to the stresses of turning, your pen will stand up to the stresses of everyday use without losing your initials.
I hope this helps!
Scott.
