I make dairy free custard with by melting nuttlex (1 tablespoon), adding cornflour (1 tablespoon) and cooking for a few minutes, adding rice milk (or soy or coconut) about 2 cups, and a little bit of cocoa maybe 1 teaspoon, stir until boiled and smooth. All the kids love it.

As an alternative to yoghurt I have mini plastic pots that I set fruit and jelly into. Great for a sweet treat and in a lunchbox. Will be back to add more later.

ETA

I have added rough amounts for this recipe, but I tend to just throw ingredients together so you may need more or less milk depending on how thick the custard is, and how thick you want it. This quantity would do for a small amount of custard for my 4 kids so increase it if you want more.