They might as well defeat him. Kushina's sealing tech are amazing and Kakashi can used his Saringan to figure out Raikage's weak point..
But if we were to compare their strength, Raikage is in different level..
Kushina has nine tail
kakashi has sharingan
so this match may probably be too hard to declare
but i am sure that Raikage will win as he has teleportation speed
hey don't forget endurance of Raikage,he can resist Rasenshuringan
and he fought Hachibi until hachibi's chakara was gone out
his punch is stronger than Gai because of lightening armor
combination with his speed,kakashi and kushina(even has kyuubi) can't match
and if even they can face,the longer the battle goes,the weaker they get
and there is one point that only few people know ,Raikage can summon Black lightening ,no one can't .Black lightening may be as strong as Amaterasu
Despite the vast gap between the Raikage and these two, I think they could win. With Kushina's holding techniques Kakashi has an opportunity to kamui the Raikage, which he wasn't hesitate to do considering his opponent. Another thing to consider-- Kakashi has a rasengan, so if he and his partner survived long enough to figure out the Raikage's weakness-- Naruto could, so he certainly should be able to-- they could beat him.