The Jews worship a god who doesn't have a son.
The Muslims worship a god who doesn't have a son.
The Christians worship a god who has a son.
If the difference between Christians and Muslims on this point imply that they worship different gods, then that exact same difference between Christians and Jews implies that they too worship different gods.
Jews and Muslims possibly worship the same god, but from the basis you have established for who worships what god, it follows that neither of them worship the same god that Christians do.
No, there is a clear difference, the Jews worship God as if He doesn't have a Son, as if the Messiah never showed up, they still follow the Old Law. No where in their Tanakh does it say that God doesn't have a Son, they just refuse to believe that Christ was the Messiah. It was the Qu'ran, which was written about 700 years AFTER the Scriptures, did they make the claim that God doesn't have a Son, the Jewish Tanakh never said such a thing. All the prophecies that the Jews were to be looking for to see the Messiah they completely missed. And they are waiting for a Messiah but the sad truth for them is, that it's too late for ANYONE to fulfill the prophecies of the Messiah, if they don't accept that it was Christ. Because the time frame has already passed by.
They too thought that Christ was a prophet and they even let Him speak in their Synagogues, but they refused (not all the Jews) to follow Christ. But there is no difference in the God I serve and the God that the Jews serve, it's the old law that we don't follow because Christ fulfilled all of that....and if you take a look at the Jewish faith, they too don't strictly follow the old law (you can also look at their Tanakh and see that they didn't always follow it then either).
You will find this verse in the Jewish Tanakh which is our Old Testament:
Psalm 2:4-9, Old Testament
He who sits in the heavens shall laugh; the Lord shall hold them in derision. Then He shall speak to them in His wrath, and distress them in His deep displeasure:
"Yet I have set My King
On My holy hill of Zion."
"I will declare the decree; the LORD has said to Me,
'You are My Son,
Today, I have begotten You.
Ask of Me, and I will give You
The nations for Your inheritance,
and the ends of the earth for Your possession.
You shall break them with a rode of iron;
You shall dash them to pieces like a potter's vessel."
and
Psalm 2:4-9 Jewish Tanakh
4 He that sitteth in heaven laugheth, the L-rd hath them in derision.
5 Then will He speak unto them in His wrath, and affright them in His sore displeasure:
6 'Truly it is I that have established My king upon Zion, My holy mountain.'
7 I will tell of the decree: HaShem said unto me: 'Thou art My son, this day have I begotten thee.
8 Ask of Me, and I will give the nations for thine inheritance, and the ends of the earth for thy possession.
9 Thou shalt break them with a rod of iron; thou shalt dash them in pieces like a potter's vessel.'
So, if the Jews deny that God has a Son, it's only by their own admission not by what the Tanakh said, for their Scripture (Tanakh) does not deny that God has a Son.