A few rather good suggestions were offered up (but the fridge was running low on options). We ended up choosing some thinly sliced cucumber, thinly sliced carrot, some chopped cos lettuce and some sliced roma tomatoes.
We added a dessert spoon of home-made mayonnaise, and a kid-sized handful of frozen corn.
After tossing it all around for a while, we added some chopped avocado and then filled up the avocado shells with the salad!
To add a bit of a tang, why not squeeze a bit of fresh lime juice on top too? Go on. Why not?