Summoning in general is a bad idea in my opinion. I mean it seems cool, but of coarse with human spirits you take them out of rest or whatever they were up to (Just because your dead, doesn't mean you can't have a social life :L )
Now with other spirits they were put there for a reason, not for you to go randomly calling them against there will. Which is never good.
Now the Dijin (More commonly known as jinn) are a Arabic Creature which can be good bad or neutral. Now it says everybody has a Jinn spirit whit them, quote "They whisper things in your ear" So basically they can make you do whatever, and you will think it's you in control. They are born of fire which is an aggressive element so i would not mix whit them all together because an aggressive element, makes for an aggressive personality.
So honestly i can think of a billion reasons not to do it really.
But your probably going to do it anyway so no the spell on this site may not be authentic. Well probably not. So writing your own would be advised. Now the words "Send them in peace or don't send them at all" Would be useful, so you may have a peaceful spirit. Now an offering would also be advised. I have no idea what a Djinn spirit would like, just make sure to let it know the offering is for it.
I don't tink the spell would work, write your own and don't summon... Call. Let them have a choice and they will most likely do you service. If tell them to something they won't listen as much as they would if you gave them the option.