I stick with everything in my above posts about the potential that Gentiles could very well have been at the festivals. In fact I am adding opening statement of verse 14 to the above list of references concerning what Peter said on the Day of Pentecost....
"Peter,...lifted up his voice and addressed them "Men of Judea and all who dwell in Jerusalem."
Then he proceeds to quote Joel:
verse 17 - "And in the last days it shall be, God declares, that I will pour out my Spirit upon all flesh..."
verse 21 - "And it shall be that whoever calls on the name of the Lord shall be saved.
Now in regards to the Court of the Gentiles, my research revealed this...
"Court of the Gentiles was the outermost courtyard and the only area of the temple where non-Jews were allowed. [Non-Jews were allowed to enter the Court of the Gentiles, but they were forbidden to go any farther than the outer court.] As its name implies, the Court of the Gentiles was accessible to Gentiles, foreigners, and those who were considered impure. There, worshippers could mill about, exchange money, and even buy animals for sacrifices. It was from the Court of the Gentiles that Jesus, on two occasions (John 2:11–12; Matthew 21:17–23), drove out the money changers, declaring, “It is written, ‘My house shall be called a house of prayer,’ but you make it a den of robbers” (Matthew 21:13).
What was the Court of the Gentiles in the Jewish temple? | GotQuestions.org
Further, in Rev 11:1,2 - Then I was given a measuring rod like a staff, and I was told:
"Rise and measure the temple of God and the altar and those who worship there, but do not measure the court outside the temple; leave that out, for it is given over to the nations, and they will trample over the holy city for forty-two months."
That court is outside the temple in Revelations 11:2...(where the Court of the Gentiles was located in Herod's temple.)
Vine's Expository Dictionary -
NATIONS: in the plural, of nations other than Israel, (Gentiles)