Parent of 4 yo here. My advice is to enroll your kid in, at least, a part time program. Or to get on a waitlist. You might thing the are okay without it now, but you also might change your mind in January. If Delta becomes truly concerning, you can keep them home. But if you don’t enroll now, it may be very hard to find a spot mid year.
Also FWIW, we did a part time, mostly outdoors program in the spring and it was so good for DC. It’s really not about academics at this stage— our DC is on track/ahead of K targets on reading writing even without PK.
But these kids have higher socialization needs than normal because of Covid. If they were in group care it wouldn’t matter, but kids home with SAHMs and full time nannies just aren’t getting enough. No PK, fewer play dates, even stuff like story times at the library, there’s just less of it. My DC really needed those months with other kids. It was hard at first but then it got better. It’s really helped in terms of getting ready for K.