Rihanna and ASAP Rocky are celebrating their son’s third birthday with a timely theme. The couple honored Riot’s third birthday on Saturday, August 1, with a Spider Man-themed bash, featuring balloons, banners and treats. Rihanna’s sister-in-law Nadia King gave fans a glimpse of the bash via Instagram on Sunday, August 2, sharing a video with decor that read “Riot 3” with fitting colors: blue, black and red. At the end of the clip, the guests all sang “Happy Birthday” to Riot. Rocky, 37, could be seen wearing a white T-shirt with a baseball hat and scarf tied around his head, while Rihanna, 38, opted for a dress. “Thanks for the invite…