Any suggestions for an alternative to pine nuts in this recipe?
Chopped walnuts often work well in such pasta dishes, as do chopped or slivered almonds.
I'd echo the walnuts.
Pine nuts and raisins are a classic combination, bur if you can't use pine nuts, almonds are an alternative. I might be tempted to try pistachios.
You can leave them out or try chopped walnuts. However I would use the walnuts sparingly.
This dish is so good that it will not suffer without the pine nuts.