hi maybe can consider home base playgroup led by experienced preschool teacher.
home environment = less germs and virus
small class size = less picking up of bad attitude and bad habits as the teacher will be able to intervene effectively.
good start for children who wants to learn and still socialize without getting shocked in school. sounds like a good transition.
plus holistic curriculum, lots of hands on acclivities which is good for growing interest in your child and learning more effectively.