I feel your pain. I happen to believe that my parish has the most beautiful, reverent, and faithful-to-the-girm OF mass in the county. But our First Communion Masses are atrocious. To be fair, there aren't as many changes as what you had - the necessary elements were all there, and recognizable. But whatever parts were extra, or unique to the first communion, were just really hard to handle. I think our pastor is in a very tough position. The religious ed program is suffering greatly, and it is really hard to find people willing to teach the classes. If he alienates the couple of people who HAVE stepped forward, and who are the ones planning the details of the FHC Mass, then what will he have left? Furthermore, many of the parents of these communicants are not familiar with church, and don't seem to be very familiar with good decorum in general. I know he is pained to try to welcome these children to the sacraments and to draw their families in in whatever little way he can. It's a tough, tough situation. Because my church otherwise does a very good job at a faithful, holy, Mass, I give them a pass on the First Communion Mass. If I am ever in a position to make a positive difference, I will, but I try to to sweat it otherwise (except for the years when my own child is receiving, and then I grieve the situation).
OTOH, my former parish has terrible First Communion Masses as well, but their FHC Mass is reflective of their philosophy as a whole. Rather than being an anomaly, the FHC Mass at this church is simply a little further down the scale of problematic than the rest of the happenings at the parish. That one was much more disturbing to me, and was the catalyst for our leaving that parish for our current one.
My point is - I would worry less about it if it is an anomaly in a parish which has otherwise faithful liturgies.
Thing is, the volunteers teaching a class are not in charge of "planning the details" of any Mass. The Church has already planned the Mass, the Pastor decides the things that are optional (what hymns or Mass setting to use, time of the Mass, etc.)