I am in a similar situation. Father of three kids under 5, I have my assembled sets and a few Rebrickable MOCs pending to be build. We (my kids and I) use a mixture of Lego cases and a storage box for them and a few organizing cases like these ones for my reserved pieces. They latch together and use a Dymo label writer to keep tabs of what is in each of the compartments. I buy them in Amazon when they are in sale for 6-8€. They are a bit bulky but at least the pieces are not laying on the floor and I can move them easily.