Sleeping on Springs

I am thinking of getting bedding sets for my children's room. Sleeping on my eldest girl's bed is like sleeping on springs. The bed that she is sleeping was bought by MIL, cheap spring mattress, for one of my BIL's for his wedding. Since then the mattress is for common use and the children's "trampoline"! But then I am quite contemplated to get one coz once other family comes back for the holiday, my children will have to shift to my room for the nights they are around. Maybe I should buy the fibre mattress instead. Long lasting and no spring will pops up.