The pair is certainly doable in a tank that large, you could even have them spawn if things go well enough. However, as with all hawkfish, the shrimp are a risk. There are better odds of keeping the shrimp alive because they were in the tank before the hawks and presumably have had a chance to grow, but that's still no guarantee. Hawkfish love shrimp, and may end up eating yours. You pretty much have to choose one or the other.