I got this recipe of Pinterest and I think it's pretty good for coloureds and dark clothes and towels.
I still use powder for whites.
I have no idea if it would work on stained kids clothes but may save some people a few pennies.
1/4 cup of washing soda
1/4 cup of borax/borax substitute (Boots or Borax off Amazon)
4 TBS of washing up liquid (currently using Aldi Silk and Lavender Balm)
Water.
I made this up in a 1.5 litre bottle which had held Waitrose Essential and I honestly cannot see any difference in its effectiveness.
The dried ingredients last for ages.