In your sandy soil it won't hurt to add the micro's.
$60 for a 55 Lb. bag. This is something you only have to think about every 5 year's or so. But if you don't do it at all, you probably won't notice it.
Don't worry about those daffodil's, the foliage and flower's are frost-proof, just don't cut the old foliage off, let it rot away naturally or you won't have flower's next year.
I would spray everything with a 2% roundup solution one week prior to planting.