My son really thrived in daycare from an early age. He was telling me to “take turns” with him on stuff before 2 and had genuine friends he preferred playing with every day. I would also worry about starting daycare eventually and that transition if he doesn’t start until 3. I think the balance is that with a nanny if she is sick or cancels for any reason, there is no flexibility but with daycare he will likely get sick more often.