We say that it is a superstition to esteem one day more holy than another, or to think that to abstain from labour is something which, in itself, pleases God (Rom 14:5, 6; Col 2:16, 17). But, following what the Lord has commanded, we sanctify one of the seven days (Gen 2:3). We devote it entirely to ecclesiastical assemblies to hear the Word of God; yet, as we have said, there is with us no Judaistic ceremony or stupid superstition. That is why we have not chosen the Jewish Sabbath, Saturday, but Sunday, following the custom of the early Church (1 Cor 16:2; Acts 20:7; Rev 1:10).
As for other festival days, we have removed them as much as possible from us, especially those which have been introduced through manifest idolatry. We have done this so as to correct the innumerable abuses which flowed from such, and to relive the poverty of many. Nevertheless, because there are certain festivals devoted, since ancient times, to the celebration of the mysteries of concerning our redemption, we use Christian liberty, and submit all to to edification, according to the different circumstances of places, times and persons.
—Theodore Beza, The Christian Faith (1559), trans. James Clark (East Sussex, UK: Focus Christian Ministries Trust, n.d.), 107–08.
As far as John Frame’s piece …”Machen’s Warrior children” I am not a big fan. I guess for many folks I’d be considered one of those warrior children. I certainly wouldn’t draw a sharp contrast between the different confessions or put them at major odds with one another. But we also don’t need to make them identical where they are not. It simply has to be acknowledged that there are some differences in the reformed confessions on minor points. Most notably for example the Westminster confession of faith is certainly more strict on do’s and don’ts in its more strident Sabbath keeping observance. Why? As best I understand it, among other reasons, certainly the Westminster divines were fighting against some things very specific at the time when they wrote their confession 100 years later. Mainly the kings book of sports certainly had something to do with all this I believe. The King Enforcing ‘The book of sports’ had folks adhering or to some degree participating (forcing the reading of it by clergy) in certain sports or festivals on the Lord’s day. This was certainly binding on the Christian conscience to demand this and the Puritans rightly were reacting to such binding. However in my humble opinion they over corrected with some of the language in the Westminster confession.
I recently read John Frame’s essay, “Machen’s Warrior Children,” and he asks whether Calvin would be ordained to certain denominations despite his view of the Sabbath; thus, he concludes that because there are differences between the Heidelberg and WCF, Sabbath observance is both appropriate and not appropriate (multiperspectivalism?). Anyway, I wonder why some put the Heidelberg and the WCF in contrast to one another? This quote is helpful, especially from Beza.
http://heidelblog.net/2013/09/are-there-two-distinct-reformed-views-of-the-sabbath/