You are not even bothering to read the authentic Hadeeths, I quoted, from Sahih Muslim and Sahih Bukhari. Read it again.. How can you assume that two girls were not so young. Read the following two Hadeeths from Sahih Bukhari...
Narrated Aisha: Allah's Apostle (p.b.u.h) came to my house while two girls were singing beside me the songs of Buath (a story about the war between the two tribes of the Ansar, the Khazraj and the Aus, before Islam). The Prophet (p.b.u.h) lay down and turned his face to the other side. Then Abu Bakr came and spoke to me harshly saying, "Musical instruments of Satan near the Prophet (p.b.u.h) ?" Allah's Apostle (p.b.u.h) turned his face towards him and said, "Leave them." When Abu Bakr became inattentive, I signalled to those girls to go out and they left. It was the day of 'Id, and the Black people were playing with shields and spears; so either I requested the Prophet (p.b.u.h) or he asked me whether I would like to see the display. I replied in the affirmative. Then the Prophet (p.b.u.h) made me stand behind him and my cheek was touching his cheek and he was saying, "Carry on! O Bani Arfida," till I got tired. The Prophet (p.b.u.h) asked me, "Are you satisfied (Is that sufficient for you)?" I replied in the affirmative and he told me to leave. (Sahih Bukhari, Book #15, Hadith #70)
Narrated Aisha: Abu Bakr came to my house while two small Ansari girls were singing beside me the stories of the Ansar concerning the Day of Buath. And they were not singers. Abu Bakr said protestingly, "musical instruments of Satan in the house of Allah's Apostle !" It happened on the 'Id day and Allah's Apostle said, "O Abu Bakr! There is an 'Id for every nation and this is our 'Id." (Sahih Bukhari, Book #15, Eids, Hadith #72)
Lets analyze both Hadeeths:
1. Sahih Bukhari, Book #15, Hadith #70:
(i) Book of hadeeth: Sahih Bukhari
(ii) Hadeeth Narated by: Bibi Aisha (رَّضِيَ اللَّهُ عَنْهُمْ)
(iii) Place of incidence: Bibi Aisha (رَّضِيَ اللَّهُ عَنْهُمْ)' s house
(iv) Who was singing: two girls
(v) Occasion: It was the day of 'Id
2. Sahih Bukhari, Book #15, Eids, Hadith #72:
(i) Book of hadeeth: Sahih Bukhari
(ii) Hadeeth Narated by: Bibi Aisha (رَّضِيَ اللَّهُ عَنْهُمْ)
(iii) Place of incidence: Bibi Aisha (رَّضِيَ اللَّهُ عَنْهُمْ)' s house
(iv) Who was singing: two small Ansari girls
(v) Occasion: It happened on the 'Id day
It is very clear that both hadeeths those Hadeeth are narrating the same incidence. Both hadeeths are similar, the first hadeeth says "two girls". If somebody want to clarify whether the girls were young or can easily do it by ready the second Hadeeth where clearly "two small Ansari girls" was used.
Furthermore, in one of the Hadeeth the words of Abu Bakr (RA) "Musical instruments of Satan", proves that it was a norm that Musical instruments were not welcomed or liked. But Prophet Muhammad (صلى الله عليه وسلم) said "Leave them Abu Bakr, for every nation has an 'Id (i.e. festival) and this day is our 'Id."
May Alah give you Hidayat (Aameen)