Is Sankalpam (formal vow/declaration) required to perform Parehani Tarpanam? Furthermore, according to our tradition, should it be performed at dawn before bathing?

After reciting “Gothrasya… Sharmanaha / Gothrayaha… Namnyaha… Mama” (specifying lineage names), one should declare “pituhuH (or mAtuH) Prathyabdhika Shraddhanga Parehani Tarpanam Karishye”. This is the Sankalpam. In our tradition, it must be performed on the next day at daybreak, immediately after completing the Pratas Sandhyavandhanam. This is our traditional custom.