You're screwed. But give it the best you got.
Actually, it is not that bad.
In fact, I wish you were here in Montreal, I would like an opportunity like this.
But I am with a 1DX.
To begin with, as someone earlier stated, if you know well the person who asked you to do the job, set his expecation and say that the images will be noisy. That will take a lot of presure off your shoulder.
I see 4 opportunities and you can use all 4 of them interchangably.
1 - when they don't move; you can go as low as 1/100th
2 - when the boy is skating (I dont' know the terminology so I would call it sliding); follow his movement by panning with the same speed and then shoot. Take the time to match the speed of your panning with his sliding then; a- when the girl is coming up or down without rotation: those can be shot with a low shutter speed as well because you pan with him (1/100th), b- when the girl is spinning: you can use whether 1/200-300th and show some blurr to show the movement (rember: he is in sharp focus because you pan with him) or higher shutter speed and freeze her (these are the ones with remarkable noise).
3 - Pan with 1/30th (or 50th at most). You will have low keeper but these are my favourites.
4 - totally freeze.
It is totally ok to have some photos with noise. Don't wory too much about it. But when you have the chance provide something without noise as well (that would be option 1 and 3 - see what DCM said). They will take the customer's worry away.
I am not sure how advanced your sport photography skill but it should be ok.
I can't guess from the video if the ISO should be 1600 or 3200 (rarely 6400) and as FTb-n said check his post, I saw some very good examples and suggestion in there.
If you are not familiar with prime, go with the 70-200 and rent a 5D mk iii or if you are ok go with the 135 f2 (but it will be a bit short often and croping will emphasize more the noise). You should crop only to corret your angles.
Good luck but most of all have fun!
You should be ok.