Really thoughtful of you.
If the PTA have funds getting a stash of nice ‘nativity’ clothes (either donated or buying some) that can be used by a whole class year after year would be great.
Uniform swops/sales at the end of each term so people can pick up what they need for the next term (even better if run on a token scheme so most would buy tokens from the office, but those who need can be quietly given some; no one on the day will know)
A month before book day/ Pudsey day/ Christmas jumper day to have a swop/donate of those too and encouraging school to announce the theme of these early eg if it’s pyjamas/spots for CIN etc so there’s time to collect items needed . If it’s spots and there are funds might be nice to get a stack of white T-shirt’s and fabric pens so kids can do their own (maybe as a lunchtime activity that week)
As an ‘eco drive’ our school did painted noses for Red Nose Day (rather than the plastic ones) which went well.
A very simple thing was at sports day moving from insisting kids bought in a tshirt in their house colour for that day was the PTA buying sashes that can be used year after year.
I guess I take view you don’t always know who is struggling and it’s better to shift the focus to making activities as inclusive and as stress-free for everyone. Some families might be money poor, but plenty of others are time-poor if they have other caring responsibilities etc
With Covid we could do donations online for things and this worked much better I thought, and the amounts coming in were similar. Certainly easier for me with 3 kids trying to find pound coins, and much less anxiety provoking for children who know there isn’t money for a donation watching their classmates hand theirs in and being worried someone will comment that they haven’t done it
Good luck, you sound just the right person to get things set up