Strictly speaking, Catholics are not 'obligated' to keep the 'Sabbath' (on earth, let alone in heaven):
2175 Sunday is expressly distinguished from the sabbath which it follows chronologically every week; for Christians its ceremonial observance replaces that of the sabbath. In Christ's Passover, Sunday fulfills the spiritual truth of the Jewish sabbath and announces man's eternal rest in God. For worship under the Law prepared for the mystery of Christ, and what was done there prefigured some aspects of Christ: "Those who lived according to the old order of things have come to a new hope, no longer keeping the sabbath, but the Lord's Day, in which our life is blessed by him and by his death"106 - Catechism of the Catholic Church (emphasis added)
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106. St. Justin, I Apol. 67:PG 6,429 and 432.
For further clarification on the Catholic view of the correct attitude to the moral law (which includes the commandment to observe the Sabbath) refer to the Catechism's teaching on the moral law.
Earthly sabbaths under the Old Covenant were a prefigurement of the true Sabbath rest that we fore-taste upon regeneration and that will be fully manifested in heaven:
3 For we who have believed enter that rest, as he has said,
“As I swore in my wrath,
‘They shall not enter my rest,’”
although his works were finished from the foundation of the world. 4 For he has somewhere spoken of the seventh day in this way: “And God rested on the seventh day from all his works.” 5 And again in this passage he said,
“They shall not enter my rest.”
6 Since therefore it remains for some to enter it, and those who formerly received the good news failed to enter because of disobedience, 7 again he appoints a certain day, “Today,” saying through David so long afterward, in the words already quoted,
“Today, if you hear his voice,
do not harden your hearts.”
8 For if Joshua had given them rest, God[a] would not have spoken of another day later on. 9 So then, there remains a Sabbath rest for the people of God, 10 for whoever has entered God's rest has also rested from his works as God did from his.
11 Let us therefore strive to enter that rest, so that no one may fall by the same sort of disobedience. - Hebrews 4:3-11 ESV
In heaven, it is arguable that 'obligation' will be an even less appropriate term to be applied to the saints generally as they are made perfect and manifest pure worship in Spirit and Truth - beholding the Lord in beatific vision in perpetual sabbath rest.
