What I meant by celebration is have a worship service, with the main emphasis on the incarnation of Christ.
This of course isn't something that the local Church requires members to attend; such as they do with the Lord Day. Yet, it is encouraged.

This is something basically that most local Churches of Reformed persuasion practice, that I am aware of and this includes St. Andrews which is the Church the late RC Sproul pastored.
Of course, there seems to be many who come out of the wood work every year; condemning this practice as totally against the RPW and therefore those who practice it not only go against the RPW; but are sinning. While some say that individuals may privately worship God and to rejoice in the incarnation. However, it is another thing for a local Church to do it.