My 8 year old's Chocolate Cake with oil

Children came home from school wanting to 'cook'. No ingredients for their usual salads, the oven was on for dinner, and the usual bulk Costco eggs so decided to let the kitchen get messy.
Prepared myself for lots of clearing up later, gave them the weighing scales, flour, sugar etc and then realised there was a tablespoon of butter in the fridge. Cue quick searching on google for butter free recipes and came up with oil as a substitute. Fortunately had veg oil (going to make puris this weekend) so plan back on track. I had visions of butter free bread passing off as cake. Apparently, oil needs liquid like milk or water to get as close to butter in a cake?
 Thankfully it worked, the chocolate cake was a bit dense, the vanilla cake surprisingly good. Not much chocolate cake in our house, husband cannot have anything chocolatey.
This is what I used - bits from various recipes and my standard sponge cake recipe;
200gms self raising flour
150ml oil
150 gms sugar
250 ml milk
2 eggs
pinch of soda bicarb and vanilla extract (soda don't think essential but I added just in case the oil flopped)
3 tbsps cocoa powder.
Baked for 45 mins at 170......
This morning, the icing, again, no fondant icing like my daughter wanted. Mixed icing sugar and water for a poor substitute. Cut a few pieces to take for her teachers/assistants. My toddler extremely worried his strawberries were not going into his tummy and to someone else.....