I heard that the pleasure of Allaah comes through the parents; is this the case with disbelieving parents as well?

All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah and that Muhammad is His slave and Messenger. 

What you heard was mentioned in the Sunnah. ‘Abdullah ibn ‘Umar, may Allah be pleased with him, narrated that the Prophet said, “The pleasure of Allah is in pleasing one's parents, and the wrath of Allah is in angering them.” [At-Tirmithi - Ibn Hibbaan and Al-Haakim classified it as Saheeh (sound)]

As-Sa’di said in his book Bahjat Quloob Al-Abraar:

“This hadeeth is evidence of the virtue and obligation of being kind and dutiful to the parents and that this is a reason for attaining the pleasure of Allah. The hadeeth is also a warning against disobeying parents and being undutiful to them and that this is a cause of incurring the wrath of Allah ... All kinds of customary dealings and all means of pleasing the parents are included in the dutifulness to parents. Similarly, every saying and action that causes the parents to become angry is included in undutifulness to them. However, if it is difficult for the child to please his parents except by incurring the wrath of Allah, then he gives priority to his love for Allah over his love for his parents, and the sin is upon the parents, so they should only blame themselves.”[This means that if the parents order him to disobey Allah, then he does not obey them in this regard. For more benefit, please refer to fatwa 84942.]

After researching the matter, we have not come across any scholar who excluded the non-Muslim parents from this. It is known that the Shariah stipulates being kind and dutiful to the non-Muslims parents exactly like the Muslim parents. The fact that they are non-Muslims does not prevent from encouraging their child to please them as long as they do not order him to commit a sin.

For more benefit, please refer to fatwas 260962 and 85180.

Allah knows best.