Humes proposed to Rochelle Wiseman of The Saturdays during a trip to the Caribbean on New Year's Eve. The couple are apparently planning to marry in March.
Sources say that Aston Merrygold, JB Gill and Oritsé Williams are touting Miami and Las Vegas as potential locations for the 26-year-old's last night of freedom.
"JLS have seriously started plotting Marvin's last trip as a free man," an insider told The Sun. "They started work on it as soon as he got engaged to Rochelle on New Year's Eve.
"Rochelle thinks it's all pretty over the top and is worried she won't be able to better it with her own group of friends. Marvin and the lads have decided it will be a no-expense-spared event with a huge group of mates and stop-offs in Las Vegas and Miami."
The insider added that the JLS boys have stepped up efforts to improve their "beach bodies", even channelling the famous 'no carbs before Marbs' mantra popularised by the Only Way Is Essex cast.
> JLS Marvin Humes 'spent £46,000 on Rochelle Wiseman engagement ring'
Watch JLS in the video for 'Do You Feel What I Feel' below: