First, it is correct that after the six days of creation, God rested from the work of creating and declared the 7th day holy (Genesis 2:1-3).  This was the 7th day of time, not every 7th day.  There was no command at this point for people to worship on the 7th day.  Also, we do not know what day of the week that was by our modern calendar - was it Saturday, Wednesday, or another day?  You see, the modern Gregorian calendar was not created until the 16th century A.D.  And Moses wrote Genesis approximately 1200 B.C.  So it is not at all clear what day was intended by the "7th day".  Even if you worshiped on Saturday, you would have no way of knowing if that was actually the same day as the "7th day" that God rested.  Also, the Hebrew people practiced the Sabbath not as our "Saturday" but as Friday Night to Saturday night, because their calendar days (not the Gregorian calendar but a 360 day a year calendar) ran from dusk to dusk. 

Second, the Sabbath day was given as a command to the Israelites under the Mosaic law (I encourage you to study Galatians 3:15-25 for context):

²³ Before this faith came, we were held prisoners by the law, locked up until faith should be revealed. ²⁴ So the law was put in charge to lead us to Christ that we might be justified by faith. ²⁵ Now that faith has come, we are no longer under the supervision of the law. (Galatians 3:23-25, NIV)

When Jesus came, the old covenant was replaced by the new covenant (Luke 16:16).  Jesus alone fulfilled the Mosaic law (Matthew 5:17-18).  It is through faith in Him, because of His death for our sins and resurrection from the dead, that the penalty of the law is no longer held against us.  We are declared righteous through faith in the LORD Jesus Christ (2 Corinthians 5:21; Romans 4:24). 

So the question would be, what is the LORD's command regarding a specific day of the week to worship?  In the article below, it is stated that the Bible gives no indication the early church met on Sunday.  But we do see a pattern of the early church meeting on the first day of the week specifically to worship and give offerings:

Note that this is not a command but a pattern of the early church.  What we are commanded to do is avoid judging people for observing worship on one day or another:

¹⁵ And having disarmed the powers and authorities, he made a public spectacle of them, triumphing over them by the cross. ¹⁶ Therefore do not let anyone judge you by what you eat or drink, or with regard to a religious festival, a New Moon celebration or a Sabbath day. ¹⁷ These are a shadow of the things that were to come; the reality, however, is found in Christ. (Colossians 2:15-17, NIV)

Obviously, the specific day of worship is not that important.  What is important is the clear biblical mandate that worship is for the whole person every day of the week:

¹ Therefore, I urge you, brothers, in view of God's mercy, to offer your bodies as living sacrifices, holy and pleasing to God--this is your spiritual act of worship. ² Do not conform any longer to the pattern of this world, but be transformed by the renewing of your mind. Then you will be able to test and approve what God's will is--his good, pleasing and perfect will. (Romans 12:1-2, NIV)

So if you want to gather for corporate worship on Saturday, that's fine.  If you want to do it on Sunday, that's fine too.  The really important thing, the most important thing, in the words of our LORD Jesus is this:

 ³⁷ ... 'Love the Lord your God with all your heart and with all your soul and with all your mind.' ³⁸ This is the first and greatest commandment. ³⁹ And the second is like it: 'Love your neighbor as yourself.' ⁴⁰ All the Law and the Prophets hang on these two commandments." (Matthew 22:37-40, NIV)