Rihanna, A$AP Rocky Celebrate RZA's 2nd Birthday, Adults Party Hard Too

Rihanna and A$AP Rocky aren't about to let their son RZA and his little friends have all the fun celebrating his birthday.

The couple's firstborn will reach the ripe old age of 2 on Monday, but Mom and Dad threw a big party for him Saturday night in NYC -- surrounded by close friends and family at the Color Factory, which features multiple rooms with different color balloons, ball pits, toy trucks, slides ... ALL the things.

Of course, RZA's parents arrived as stylish as ever!

Rihanna was wrapped in a light blue/gray fur stole as she carried 9-month-old Riot Rose, and A$AP was rocking a blue pin-stripe button-down and shades as he ushered in the guest of honor.

It appears the party kept going well after the kids went to bed -- some videos on social media captured Rihanna and A$AP having a good ol' time in a club ... conga line dancing and RiRi even had a mic in her hand!