Matthew, several years ago, a member of my extended family died and her children had a NO "funeral mass" in the chapel of the nursing home where she had lived. An SSPX priest I know said to go out of respect for our family, but to not participate in any way, so I took my missal, sat in an inconspicuous place, silently read my missal and silently prayed a rosary for the repose of her soul. I had not been near a NO church in many years, and the whole thing just repulsed me. It was more like a party than a Catholic funeral. The saddest part of it all was that she loved Tradition and never went to a NO mass in her life. 
More bad advice from the SSPX. One should never attend a sacrilege out of concerns of human respect. There is a much higher principle involved in this.
Out of Catholic Charity in such cases one should not even consider a Novus Ordo funeral, but rather attend the graveside internment, pray the Catholic prayers for the dead, and say a Rosary for the repose of that soul. In this way you fulfill your Christian duty and do not violate the Sensus Catholicus and the principles which come from it.
If I recall correctly, even Archbishop Lefebvre attended a Novus Ordo wedding of a relative...
It is my understanding that the 1917 Canon Law allowed for Catholics to attend non-Catholic weddings and funeral services so long as they did not actively participate.
That is a pretty thin justification to attend the Novus Ordo. A Protestant service is nothing, it has no meaning or power. The Novus Ordo on the other hand is a mockery of Our Lord's Sacred action and a sacrilege. The 1917 code never imagined such a thing to be possible and
canon law is not Divine law which forbids it.