I am very surprised that your question in the OP was not ‘what can I get my parents with very little money?’ But ‘has anyone else done this?’ It comes across as asking for validation rather than solutions.
Because obviously it is a problem. It isn’t about the money that you spend on anyone. It is about the thought. And it appears, and will appear to them unless you fix it, that you just didn’t think about your parents.
And obviously there are solutions. With effort over the next few days you can really change the Christmas you will all have. Some suggestions:
Salt dough decorations you can make with your DD.
A photo of them and you daughter
Biscuits or cakes you can make
Home made vouchers for a trip in the new year, or an IOU for something they would prefer to choose themselves (eg to get slippers in the right size, for example)
A photo of you and then from when you were little, in a frame with some thoughtful words.
A well chosen book from a charity shop.
Christmas decorations eg dried orange slices, cinnamon sticks tied with a ribbon, cloves stuck in an orange.