Austin Butler and Vanessa Hudgens
05/16/2013 at 10:10 AM EDT
and boyfriend Austin Butler
couldn't keep their hands off of each other over the weekend.
The pair, who kicked off Saturday night by dining at new hotspot Hakkasan Las Vegas were joined by Kelsey Grammer and wife Kayte Walsh
, who were all celebrating a mutual pal's birthday.
In a nearby private dining room was Ke$ha, who threw a surprise party for one of her creative directors.
When Hudgens's table was done eating, her group then gathered in the main room of the venue's nightclub, where they sat at a VIP table next to the deejay booth – and her PDA with Butler began.
"The couple was very cute together," an onlooker tells PEOPLE, of the black mini-dress-clad actress and her The Carrie Diaries
beau. "They were seen dancing a lot
throughout the night. They were sipping on cocktails and being cuddly and affectionate and were spotted kissing non-stop throughout the evening. They were listening to the Bingo Players, who deejayed that night."
– Dahvi Shira