Mumma it depends how old your dc's are but really I don't think it's about how much, it depends what they have asked for, is there one thing they would really like? You don't have to go over the top, you don't need to compete with what others spend. Don't buy things just because they are on offer. Write a list and stick to it or things get out of hand (talking from expereance), just buy things you know will get played with, things they really want. I stay of the bargain threads to stop me buying things that are not on my list.
I spend a different amount each year as it depends what they want, my dd's are almost 12 and 14, this year I have probably spent around £250 each but they only have around 5-6 gifts, main present costing £130, some clothes and a few other bits they want/need.
I spend £30 on my mum and the same on my dad.
All other children in the family I spend around £10 each
I don't buy for any other adults other than my best friend (around £15).
I try and budget for £1000 to cover everything including food.