Yes, looks good! I'd stick with that.
As an aside, a convention seems to have grown up in Middle Earth gaming that wargs are ridden by smaller orcs. I don't think Tolkien's writings support that: Beorn pulls Bolg down, which implies strongly that he was mounted; and the Isengarders use wargs (a straight reading of The Lord of the Rings suggests that the Isengarders are all, or mainly, Uruks). So, given that the Oathmark goblins are a good size for Uruks (or the equivalent large orcs from earlier Ages), I'd stick with them for your wolfriders.
The little Ral Partha ones are lovely, though - look what John Blanche did with them!
Yes, I think this seems the best option for mounted orcs/goblins. If I wait for Oathmark to come out with wolf riders I will be waiting some time.
I agree with the wargs/small orcs comment. As n orc leader I would mount the biggest orcs a wolf could carry and use them as shock cavalry. It would be a wast of savage fury to use a warg as a mount for
horse wolf archers.
I did like the look of the gargantua orcs from Ral Partha, but these are a bit too GW looking and too big. Ral Partha were happy to supply just the riders (which are normally mounted on lizards).
Ensign Madcap, I forgot about that particular Schleich wolf. The pictures of it always make it look a poorly sculpted figure, but it might just be in need of a (semi-) decent paint job.