Acceptable amount to pay someone

What is an acceptable amount to pay a immediately family member (my parents, my grandmother, my siblings) to watch my 2 kids (2 & 4 years old) while I work a 8 hr shift once a week

Edit : it wouldn’t really be once EVERY SINGLE week , just whenever I wanna pick up extra shift

Edit : $100-140 will be too much being as I am a single mom making $11/hr . That extra shift would be pointless because I’ll be making only $88 but paying $100+ on child care . I wouldn’t really be profiting anything .