What abilities do I most want to build in the early-childhood and school years?

There's no single right answer, but many professional bodies emphasize as a foundation: (1) a secure relationship with people (attachment), (2) communication—conveying and receiving, (3) daily-living skills (eating, dressing, toileting), (4) regulating emotions, and (5) play and interacting with people. When these "living-and-relating abilities" grow before reading, writing, and arithmetic, later learning also builds up more easily. Grow them little by little in daily life, matched to the child's developmental stage.