fold his fingers / make a hand gesture for / make a

A: How old are you?

Toddler: (unintelligible)

A: What's he saying?

Parent:

He wants you to help him fold his fingers into a two.
He wants you to help him gesture "two".
He wants you to help him make a hand gesture for "two".
He wants you to help him make a "two" with his fingers.

How do you say it?

He seems to be showing a "V" sign with his fingers.

tedmc said:

He seems to be showing a "V" sign with his fingers.

Click to expand...

Over here, this is how children are taught to count:

tedmc said:

He seems to be showing a "V" sign with his fingers.

Click to expand...

No, he isn't.

The 'V' sign is made with the back of the hand towards the person to whom it is shown. (Note: this is an obscene gesture.)

With the palm facing outwards it's the 'victory' sign, or the number two.

not a teacher

"What's he saying?"

He's saying/making "two" with his fingers.
He's showing/telling you "two" with his fingers.

If he is in fact asking for help, then your last suggestion seems the most natural.
I would probably say: He wants you to help him make "two" with his fingers.

Rover_KE said:

No, he isn't.

The 'V' sign is made with the back of the hand towards the person to whom it is shown. (Note: this is an obscene gesture.)

With the palm facing outwards it's the 'victory' sign, or the number two.

Click to expand...

It could be either, according to:

http://dictionary.cambridge.org/dictionary/english/v-sign
https://en.wikipedia.org/wiki/V_sign

I attached the image simply to help teachers picture out what's going on, and not to spark a debate as to what the child is actually gesturing.