Fr. Z offers a great deal of commentary here as he refutes an article in US Catholic, a less than orthodox publication. The bottom line is canon 844:
“Catholic ministers may licitly administer the sacraments to Catholic members of the Christian faithful only and, likewise, the latter may licitly receive the sacraments only from Catholic ministers.”and
“Whenever necessity requires or a genuine spiritual advantage commends it, and provided the danger of error or indifferentism is avoided, Christ’s faithful for whom it is physically or morally impossible to approach a Catholic minister, may lawfully receive the sacraments of penance, the Eucharist and anointing of the sick from non-Catholic ministers in whose Churches these sacraments are valid.”Protestant sects do not have valid sacraments. Canon 844 cannot be used to justify receiving communion from Lutherans, Methodists, Episcopalians, etc. The non-Catholic Churches that do have valid sacraments are the Eastern Orthodox Churches, the Polish National Catholic Church, and the pre-Calcedonian Churches.
Also, attending the liturgy of a Protestant sect cannot fulfill a Catholic's Sunday obligation to attend Mass. Refusing to attend Protestant services can create family tensions. However, it is not unreasonable to expect our Protestant family and friends to respect our Catholic faith. Perhaps you can attend Saturday evening Mass and then spend Sunday morning at the Protestant liturgy (refraining from taking communion as described above). Or perhaps you can attend Mass while the others attend their services and then meet for brunch.
Our Protestant relatives are welcome to attend Mass, but just as we do not receive communion in their churches, they should not receive the Eucharist at Mass. No one, Catholic or Protestant, should receive the Eucharist unless he is in a state of grace and fully united to the Catholic Church. Such unity is impossible for Protestants.
It is tempting to pretend there are no differences for the sake of peace in the family. However, we miss a chance to evangelize when we fail to live up to the teaching of the Church. We also risk confusing children in the family. The Catholic Church is not just one of many Churches. It is the One Holy Catholic and Apostolic Church. There are elements of holiness in many of the Protestant sects, but only the Catholic Church contains the fullness of truth. By insisting that all Catholics attend Mass on Sunday (or Saturday evening) and refusing to engage in "cross-communion" we show by our actions what we truly believe.