Cost opinions!

My husband was recently layed off and is looking for work, i have been thinking about going back for a while now. I have 2 kids ages 3 years and 5 months old. Daycare for both of them is out of the question but my best friend is willing to take them both for an agreed upon number

Me and her had an agreement that $400 a month is a fair amount but her husband says its not enough and my husband says its too much

I will be providing breakfast, lunch and snacks as well as toggling cost of pre planned outings once a week. I think 400 is more than fair as she stays home with her kid too and has no intention of going back to work, she doesnt pay extra costs of a facility of utilities as shes in a rental suite with utilities included, she wont be providing food. Just warming up lunch and supervising the kids until either i or husband comes to grab them

Does this seem like a fair number?