Much of DIII recruiting is done by player contacting the school and showing interest. There is this misconception that all the DIIIs recruit heavily. Of course, there are a few DIII that do recruit hard, but the majority take what they can get. If you contact a dozen DIII schools expressing interest, you will see for yourself that they will also express interest in you. I've often wondered why players spend money to attend showcases to get a non scholarship college interested.
There really isn't much reason to attend a showcase, especially one that will cost you a lot in order to find a DIII school to play baseball at. Most important is that the player qualifies for admittance.
Would you have the same advice for a US-based kid? If DIII schools are on the list of colleges that attend programs like Headfirst Honor roll camps, then is it safe to assume that they fall into the group of DIII schools that do recruit, and that in those cases just emailing and applying is not enough?