Actually, you have two problems here. Let’s take them in order:
[quote=johnboy]My Catholic daughter is married to a Methodist. They have agreed to raise their three daughters Catholic. Her husband wants her to attend his church since he occasionally attends hers. She asked her priest if she can attend the Methodist service in lieu of the Mass “occasionally.” The priest gave her a dispensation to do so.
The priest had no authority to grant your daughter permission to skip her Sunday obligation in favor of a Protestant service. She could be granted permission to attend a Protestant service occasionally in addition to satisfying the Sunday obligation at a Catholic church, but the Protestant service cannot *take the place of *attending Mass.
In other words, it would be fine if your daughter and her children went to the Saturday Vigil Mass to honor their Sunday obligation to attend Mass and then accompanied your son-in-law to his church on Sunday; but skipping Mass altogether for a Protestant service is not permitted.
[quote=johnboy]Now she is receiving the Methodist communion in order to “fit in” and “keep peace in the family.” She understands that the Methodist communion is a symbolic gesture and feels her mind is properly disposed to receive it. My wife and I understand the pressure she’s under, but don’t think it proper missing Mass and believe her children will be confused. How can this be resolved?
This is a separate can of worms.
Am I sinning?
Wanting to “fit in” and maintain “peace” are not sufficient reasons for a Catholic to receive an invalid Communion. Your daughter can certainly pray for spiritual communion with our Lord during communion time at the Methodist church, but she cannot receive Protestant communion and remain faithful to her Catholic obligations, both to herself and to raising her children to know and follow the Catholic faith.
For information on permitted forms of participation by Catholics in Protestant services, please see the document linked below.
Directory for the Application of Principles and Norms on Ecumenism