Wishes is the nightly show/fireworks at MK. At California Grill you can view with great seating while enjoying your meal. They dim the lights very low and pump in the music directly from MK. It is amazing!!
We ate at Cali Grill during the Xmas fireworks, and it was great to have a chance to see them because we were not staying at WDW long enough to attend the Party. The food was good and we were glad we were able to see the fireworks so conveniently, but we didn't think the food merited 2 credits. I'd choose your latter option. I haven't eaten at Via Napoli but 'Ohana is great - DH's favorite dinner spot.
If you want to watch Wishes from a cool viewing place then CG is awesome, and the food is great too. I haven't tried Ohana yet and if you want to try Via Napoli I'd just spend out of pocket.
California Grill!! The food is amazing, the view and the fireworks are awesome. Via Napoli is great and delicious, but not worth 1 point vs paying out of pocket (buy a large pizza between two! You'll be too full for dessert on the DDP anyway lol!). Ohana is really great, but also a set price so maybe pay out of pocket for that? California grill is expensive!! But worth it. So the points would be well worthwhile spent here.
Honestly CG was the best meal I have had not just in Disney but anywhere- and then there's the view and the fireworks to boot!
I would go with Cali grill. I really like via Napoli, but have found that Ohana has declined over the past few years. Cali grill is a great meal, and a nice, more romantic setting than the other two choices.