This topic should definitely be in IMHO, as there is no single topic about which there is a greater fund of vociferous ignorance on display at the SDMB than chiropractic.
Some facts, though, as this is GQ:
A bit of logic, please. Beware hysteria. If chiropractic were pure bunk, pseudoscience, quackery, bullshit, voodoo, etc. etc., it is unimaginable that the Boards of Professional Regulation in all 50 states and DC (District of Columbia) would license doctors of chiropractic; it is just as highly unlikely that large numbers of major league sports franchises would have chiropractors on staff or trust their multi-million-dollar athletes to them. Also, chiropractic doctors are found at all Olympic Games, major boxing events, pro tennis, martial arts championships, etc. There are VA hospitals with DCs (doctors of chiropractic) on staff. There are an increasing number of neurosurgeons and orthopedic surgeons who work side by side with chiropractic physicians to deliver manipulations under anaesthesia in severe cases. The list literally is too long to put here but you get the picture.
Yes, Virginia, there are people practicing chiropractic who should not be. These individuals we call quacks. Just as there are quacks cutting off the wrong leg, leaving surgical implements inside their patients, and outright killing their patients through a variety of means from negligence to misdiagnosis to poisoning to all manner of incompetence. Thankfully, in both cases these miscreants are in the tiny minority, and most doctors (DC, MD and DO) are not crackpots. Health care is not an exact science, but those who are crackpots are rightfully derided by their peers who are more scientifically minded.
–Won’t my child DIE if I take him to the chiropractor? Relax. The risk of death as a direct result of chiropractic adjustment or manipulation is vanishingly infinitesimal compared to the risk of death due to medical malpractice or being struck by lightning five times. This is partly because, as crisis intervention specialists, medical doctors typically see patients who have much more dire illnesses than chiropractic patients have. Many parents swear by chiropractors for ridding their children of bedwetting, for example, after years of other alternatives (including MDs) had failed. Often the results are dramatic, after just one or two visits. It took me two adjustments to eliminate my stepdaughter’s headaches at age 10. Why does it work in these types of cases? I honestly don’t know, and I’m not entirely sure it is knowable. As long as we do no harm and deprive the patient of no necessary medical care, we have nothing to lose by giving non-invasive, non-poisonous, conservative therapy a chance to assist the body in its quest to normalize itself. If it works, fine. If not, then it makes rational sense to go to more stringent measures. (Give it a fair chance. A few, say 5-12, visits–not 500.)
–Can chiropractic boost the immune system? This is not known with a reliable degree of certainty. A properly funcioning nervous system, however, would certainly not be expected to hinder the immune system, but rather just the opposite.
–Do chiropractic students get any training? The first two years are identical to medical school in terms of gross anatomy, dissection and hard sciences; the second two focus on radiology, clinical diagnosis, laboratory testing (as in med school) plus physical manipulation instead of pharmacology and surgery.
–What about the infection? If it’s an infection, it’s a medical problem and not simply a chiropractic one in my professional opinion. Claims of curing infections, cancer, epilepsy, AIDS, hepatitis, etc. through physical manipulation, while exceedingly rare, make headlines because they are absurd. Once something is infected, it has reached what I consider crisis stage and needs to be arrested immediately, though any reliable means possible. The body does try to heal itself, but sometimes it needs urgent assistance such as drugs or surgery, which chiropractic physicians, by deliberate choice, do not employ. I recommend seeking competent medical advice for your child’s chronic ear infections along with the adjustments, and if you are at all uncomfortable with the therapies suggested, get a second opinion from another physician. (If needed, your chiropractor should be able to recommend several competent medical doctors in your area whom he or she works with when referral is indicated.)
–You seem sane and scientific; why isn’t the truth about chiropractic known more widely? Because it is inconceivable that there could be an organization on earth more piss-poor at public relations and image communication than the chiropractic profession. There’s some infighting and civil war going on between opposing associations that does nothing but waste time and money. Meanwhile, 110 years later, intelligent people in the general public are still repeating nonsense and half-truths they’ve picked up from other laypeople no more knowledgeable than themselves. You can tell the profession pisses me off–but that does diddly squat to change the fact that it’s a viable healing art with a vast and growing body of scientific evidence to support its effectiveness in a range of cases, chiefly but not exclusively neuromusculoskeletal in nature.
–Despite all that, will other people still continue to cut chiropractic down with a quasi-religious zeal? Probably. 
Hope this helps. Good luck to you and your child–I hope everything works out well.