Hello Steff, considering what to do with donations, you could use it to buy items/stuff to enrich your roleplay with it. You could also fund events/equipment related to your corporation to it.
I've been running the Arcology for a while (albeit only serious for the last few months) and I've got suprised by the generosity of alot of people. Usually people donate civilians to me (wich is great as I ask for them) but I also ran into your issue, where people donated isk & goods/equipment. At first I didn't really know what to do with it, but now I choose to use it to enhance my RP.
With the isk, I usually try to spend it on interesting stuff to enhance RP, or equipment (examples: antibiotics, as reflection of a medical examination before entry; Wheat & water as foodsupply etc ) People like it when you can link something in chat (I could suggest to look for dolls for your orphanage)
I also plan to fund events/RP orders with it (currently in the proces of 'worldbuilding' in null, wich will be reflected by buy orders and depending how fast or how much they get filled, the story develops from there )
I generally assume that people who donate isk to an RP project would like to see it spend on stuff related to it (this can even be ships you almost exclusivly use for this)