A condition for granting permission to marry a non-Catholic is that the Catholic Christian party undertake to remove dangers of defecting from the faith and to do all in his or her power so that all the children are baptized and brought up in the Catholic Church; the other party is to be made aware of this undertaking

Can a Catholic attend a wedding not in a church?

All Catholics may attend, but with reservations. Fulfills natural law and canon law. On occasion a practicing Catholic will fall in love with a non-Catholic and wish to get married in a non-Catholic church because — for instance — the spouses father is the minister of the local Protestant congregation.