Newbie clay advice

Hi all, so I've been doing up a vintage wooden dolls house, and I'm turning it into a witches supplies shop on the ground floor, with a one bedroom home on the top two floors. I'm going to be adding on extra rooms to the side of it higgledy-piggledy, as there's only one room per floor on the original house, and I'll be putting in a garden at the side. When considering support for the added on rooms, because I'm adding on to the second and third floor but not the ground floor, I was thinking I would make a large tree coming out of the garden and wrapping around the side of the house, which would help hold up the added on rooms and give them extra support so they don't fall off, as well as just look super cool on a dilapidated witches shop and house! I was thinking about using scrunched up tin foil and wooden dowels as the skeleton of the tree, and then covering that in clay, and then painting that once it looks enough like a tree, but with it being so large, I'd obviously need to use air drying clay as it wouldn't fit in the oven, and I wouldn't want to put a vintage wooden dollhouse in the oven anyway! I'm a complete newbie when it comes to clay, I've literally never used it before, so I don't know if A: clay is the right medium to use for this endeavour anyway, B: if air-drying clay is the right type to use if clay IS the way to go, C: if clay can be painted over with acrylic paints, and D: how do I even start going about this to begin with?! Usually I jump in headfirst with my creative ideas, and usually they come out really well, but this particular one is my passion project, my baby, the thing that keeps me up at night with all of my ideas and plans coming together, and I really really don't want to mess it up! Any advice would be very gratefully received, thank you all so much!