Grammar help for a 6-year-old: correcting “What toy is there fourteen of — balls or cars?”

Correct, simple sentence: Are there fourteen balls or fourteen cars?

Why this is better (in simple steps):

1. Use Are there when you talk about more than one thing. ("There are" for many items.)
2. Say the number before the thing: "fourteen balls" or "fourteen cars."
3. Ask the two choices clearly: "Are there fourteen balls or fourteen cars?" is short and easy to understand.

Another OK version: Which toys are there fourteen of — balls or cars?

The original sentence sounds a little odd because it mixes singular word "toy" with the idea of many items. The corrected versions use plurals and sound natural.