I'd be curious to hear of Gordon has any input on this.
I haven't had it in awhile. Last time I think I tried it was when I reviewed it in Zymurgy. I remember thinking it used to be fairly sweet (a common fault with tripels) but that the one I sampled had dried out nicely. It went on the BJCP examples list in the next version after that tasting.
Your recipe looks fine. Mine is a bit more simple. See p. 36-37. I'm shooting more for a La Rulles Tripel than a GM, so who knows how the balance might work?
1762 is Rochefort yeast. Should work fine. Sometimes it's a slow starter, but if you have a proven slurry, that should be fine. I think the Ardennes yeast (Achouffe) would work, as would the Westmalle or Orval yeasts.
A little coriander is ok. Westmalle uses that (or at least used to, not sure if they still do). Many Belgian ales use it. Just go light. It gives a lemony aromatic character. You shouldn't be able to pick out the spice as coriander. It should just add complexity.
Not sure how many IBUs this has. I've had Tripels that have seemed sweet even though they are well-attenuated. The problem is the IBUs are too low.
But that's my taste. Some people like tripels to taste like big belgian Blond ales.
I do recommend not going huge on the OG, otherwise the FG would be too high.