Thought it may be useful to share some experiences from the UK. As foster carers we get an extra allowance at Christmas, at the child’s birthday and at the start of the summer vacation. It’s significant, about $200 on each occasion.
We have used it to fund parties and experiences as well as gifts. Many of our placements have an unusual relationship with “stuff” from previous family history. Sometimes they were given too much, other times possessions were taken back and resold, other times gifts were broken due to feelings of unworthiness.
So I would be wary of only giving things. Ideally gifts should be individual, chosen by those close to the children. We took a four year old to the seaside and funfair for the first time. We gave a seven year old a bike for Christmas, that gave her an experience of learning a skill and a sense of freedom.
But anything that brings joy or inspiration to kids in care is a worthy cause. Good luck!