I have no experience.
I read one coach say you can expose them as early as 4 or 5 (as you've said) but you can't really start teaching them until around 7 or 8, and he questioned if starting as early as 5 was worthwhile.
Don't remember the source, sorry for that, but it's something to consider.
I have been reading biographies of many chess players and it seems like many got exposed to chess at the age 4-5 with some as early as 3 (Polgar sisters, Capablanca etc). How early is too early for chess? I have 2 years 9 months son and 9 months daughter and I just cannot wait to start teaching them. My son has been exposed to chess from birth (saw me play, saw me teach kids, saw zillion of chess boards in the house, also saw chess on digital devices). He knows the names of pieces in russian and English but he is still too young to play or understand. Any of you have experience with teaching pre-schoolers?