My view is that Bioinformatics/Computational Biology is not a bubble, simply because these disciplines do not reflect a *job market* but rather a shift in how all of biology will be done in the future. Just as molecular approaches transformed the way biology is done during the 1970s-1990s, computational approaches will likewise transform how biology is done in the 21st century. And just as molecular techniques in biology have not (and will not) go away any time soon, neither will computational techniques. The crucial thing to recognize is that there is still a relative underrepresentation of *good* computational biologists (i.e. with strong skills in biology AND computing) so I would strongly recommend this career path for your son.
For more on why I think PhD students and post-docs should train in computational biology, please see: (Top N Reasons To Do A Ph.D. or Post-Doc in Bioinformatics/Computational Biology). Some of these should apply directly to undergraduates, and should factor into his decision making process for the long-term.