My Mum resigned her job 8 yrs ago to help take care of my 3 children (now youngest one being one month old). I gave her $1500 pm on top of monthly allowance. The two elder children are now in primary sch so just need her to pick them up from bus stop where sch bus is alighting them at + buy lunch for them.
I’ll say $550-$700 for your mil cos after all — she’s your mil and not anyone else. You will have a peace of mind at work. It’s about the same $$ if u put ur child at child care center 1.5 yrs old onwards.