His wife does not want to wear hijaab
      and he fears for his young daughter
Question

                My wife is not wearing Hijab although she is a strong beleiver and practicing all Salats on time etc. We are both Engineers and we have 2 young daughters (2 and 5 Years. I am worried that my children will also go away from wearing hijab if they see their mother not wearing it as well. I've tried many times to convince her to put it (she has read the relevant sourates) but I've stopped doing that when I felt that she would reject whatever she was already on. 
My question is as a husband and father, shall I force her to wear it anyway to preserve the future of the daughters or shall I keep patient untill Allah guides her? 
My second question is are we (the husbands) responsible in front of Allah regarding weather or not our wives / daughters wear hijab or not?
Praise be to Allah.Strong
      faith must have effects which can be seen in a person's appearance and
      conduct. If a person persists in sin, this is a sign of weak faith.
 What
      you have to do is try to plant the seeds of faith in her heart and help it
      to grow strong. What is meant by that is the kind of faith that will
      motivate a person to behave in accordance with the sharee’ah. Then try
      to instill in her a love of the hijaab and of righteous deeds, such as
      explaining the benefits of hijaab and how good it is, and giving her books
      and audio tapes, if these are available, which speak about that. One of
      the most important means which will help to achieve this is to put her in
      touch – in an indirect manner – with righteous women who wear the
      hijaab and try to have frequent family gatherings with righteous
      relatives.
If
      you do this, you will have tried various means of convincing her. Then you
      will have to oblige her in an appropriate fashion and not allow her to go
      out to public places without hijaab. (It is important to explain to your
      daughter that hijaab is obligatory and tell her about Allaah’s ruling on
      hijaab, even if she realizes that her mother is falling short. You have to
      explain it to her at a level that she can understand so that she will see
      that there is a difference between the rulings of sharee’ah and the way
      her mother is behaving. Who knows – perhaps she will advise her mother,
      in the moving and innocent manner of children – to wear hijaab).
 With
      regard to the second question, there is no doubt that fathers are
      responsible if their wives and daughters do not wear hijaab and do not
      adhere to the rulings of sharee’ah, as Allaah says (interpretation of
      the meaning):
“O
      you who believe! Ward off yourselves and your families against a Fire
      (Hell) whose fuel is men and stones” [al-Tahreem 66:6]
And as the
      Prophet 
 (peace and blessings of Allaah be upon him) said:
“Each of you
      is a shepherd and is responsible for his flock… the man is a shepherd
      over the members of his household and is responsible for his flock…”
But if a person
      does all that he can and strives his utmost, but does not achieve any
      results, Allaah will excuse him and will not punish him; on the contrary,
      He will reward him for his efforts, and Allaah does not cause the reward
      for any good deed to be lost.