The local Franciscans have everything to do with that. You would need to study the "Franciscan case" in this whole matter to understand what is really going on. Basically they have been disobedient to Rome concerning a settlement reached in the mid 70's whereby they refuse to give up parishes to the secular clergy under the Bishop.
The then children came around with a practical joke which the Franciscans ran with...
There's a saying which I think is a useful measure of gauging apparitions. "Vox populi, vox Dei". What this means is that popular devotion will often give a verdict on an apparition before the Church officially pronounces. Lourdes and Fatima were cases in point. Both had a strong and devoted following before the Church officially ruled. The same often applies to saints and holy people. Padre Pio and Mother Teresa, for instance, were already well established in popular devotion before the Church officially ruled on their sanctity.
Before anyone raises the point, I'm well aware that this rule does not apply to Church dogma or teaching. However, with regard to supernatural happenings which do not form part of the deposit of faith such as apparitions and the sanctity of those whom we deem holy, it's often a good guide.
For this reason, I'm rather skeptical of the "practical joke" hypothesis. There are fakers and kooks all over America claiming to see Jesus or His Mother. They never achieve critical mass (no pun inteneded) nor accumulate a worldwide following as Medugorje has.
There's something supernatural happening there. And the basic message of "prayer and fasting" seems to me to be a gospel one.
Of course, I've been wrong before and will be again but that's just my 0.02. As always, I'm totally amenable to whatever the Church's official verdict is......if there ever is one.