In terms of power, the Saiyans should have enough to take this if they can all hit Boo with their best Ki attacks simultaneously, but that's a pretty big "if". Even though we didn't see the extent of this Boo's regeneration, there's no reason to believe his is any less when a Boo of lesser power like Good Boo regenerated as well as normal and Pure Evil Boo's fighting style presents him as both serious and opportunistic. Considering Vegeta isn't the type to perform teamwork well and Gohan's skills are incredibly rusty, it's very likely Boo would capitalise on these to throw off their teamwork and pick them off individually, likely using his chocolate beam.