Question:
Would a man be permitted to babysit for his own 4 year old and 3 of her five year old friends if no one else is home?
Answer:
There is a dispute at to what is the minimum age a girl can act as a shomer (guardian) and what age they have to be to allow seclusion with 3 of them. Since the girls are too small according to many opinions I would suggest that during the day or the early hours of the evening keep the door slightly ajar, but if it is late at night should ask 2 neighbors to drop in unexpectedly.
Sources:
Bach E:H 22, Hamakneh Kiddushin 82a, E:H 22:9&11, Dvar Halocho 4:3 quoting the Chazon Ish &10:5, Teshuvas Tzitz Eliezer 40:16-5, Teshuvas Shevet Halevi 5: 204-1 &10:237.Teshuvas Vehanhogos 2:658-2
