I hate to say this, but this is not acceptable to the Orthodox Church. Attending services in a heterodox church is unacceptable, in this case would mean automatic excommunication for the Orthodox spouse and I’m not sure how the Catholics would handle this. Having your children baptized by the heterodox is another serious sin and would again be an automatic excommuncation. Orthodox parents are under full obligation to raise their children in the Church, no expections ever. You could marry a Roman Catholic in the Orthodox Church as the RC baptism is acceptable. However, an Orthodox Christian is required to attend Othordox services and raise their children in the Church. So this isn’t a compromise, as far as the Orthodox Church is concerned this person has left the Church. He would have to cease these practices, confess these serious sins, and perform the required pentence (probably a number of years of excommunication) and only then could he receive the Eucharst in the Church.