You should talk to the parish priest first, then he will not correct liturgical abuses, start writing, first to your bishop, and then if this does not solve the problem, then to Rome. Here are some guidelines about writing to them.
wdtprs.com/blog/tips-for-writing-to-bishops-and-to-the-pc-ecclesia-dei
While standing during the Eucharistic Prayer is a liturgical abuse, holding hands then is not, unless the priest tells the people to hold hands during the Our Father, which is out-of-line.
However, if you do write, it would be better to speak of other liturgical abuses as well, especially of more serious ones, if there are some.
If you are not sure if something is a liturgical abuse, you could ask on this thread.
Liturgical abuses do not make a mass invalid, but you have a right to be upset over liturgical abuses. The Vatican has said very definitely and more than once that liturgical abuses violate the rights of the people there. It also in fact disturbs the worship of the people there who realize that something wrong is occurring during the mass. The Second Vatican Council insisted that priests have no right to alter the liturgy in such a way
(As another poster mentioned, the Church’s GIRM(General Instruction on the Roman Missal) instructs that the people are to kneel during the Eucharistic prayer. No priest has the right to change this. [Nor in fact can even the local bishop change this, since it is a Church norm and not a diocesan prerogative].)