Bhāgavata Purāṇa describes how Yaśodā and Nanda Mahārāja celebrated Krishna’s first birthday. All the learned brāhmaṇas were invited, and they chanted Vedic hymns for the good fortune of Krishna. During the chanting of the Vedic hymns and playing of the bands, Krishna was bathed by mother Yaśodā.
You can also perform abhishekam to Lord Krishna on the auspicious day of Janmashtami. You can also arrange for Hare Kṛṣṇa kīrtana and chanting of Śrī Brahma-saṁhitā prayers during the abhiṣeka or just chant the Hare Kṛṣṇa mahā-mantra.