Thanks for mentioning your prior research :-)

Manure is fresh, medium, or aged. So if it was fresh (hot as it is sometimes called) it can burn new plant roots. If it was medium and distributed well throughout the soil, it will most likely be ok. You can actually lay your hand against a sack of manure and if you feel heat, you know it hasn't aged enuf for contact with plant roots.

I assume it was cow manure.

Since you have sandy soil, I would definately add bonemeal and if I had it some all purpose bulb food (low in nitrogen) because nutrients don't bind well with sand. The bonemeal is not available to plant roots this year but will slowly become available (which is why it is so nice to use for future feeding). Adding soil, organic material, and manure is wonderful for sandy soil.

I dig fertilizers, etc. into new beds about a month prior to planting.