Wa alaikum salaam wa rahmatulahi wa barakatuh,
It is a very sad situation when children go astray from the path despite efforts to guide them aright. At the same time, we know the importance of maintaining family ties. However, when family members are not behaving in accordance within Islam it becomes difficult to maintain ties.
Even though your daughters are older now, you can still have a positive influence on them and are still responsible to try and guide them. Unfortunately, they have met people who don’t seem to be a good influence on them, but that doesn’t mean that they will never come back to the straight path.
At the very least, continue to pray for them. Make du’a that Allah will turn their hearts and guide them.
Cutting them off may only contribute to them straying further from the path as it could make them feel bad towards Islam as it is the thing that caused the divide between you and them. Instead, it is better to be a good role model to them as you have been throughout childhood. Let them see how beautiful Islam is and how much happiness it brings you. If you are not comfortable to have such a close relationship, you can still do these things through minimal contact.
This will further have an impact on your boys who you are presently most concerned about in a positive way. Similarly, the current situation may also taint their view of Islam in the same way as it may do with your daughters. It is possible that they may also come to see Islam as a thing that has caused a divide in the family resulting in them not seeing their sisters.
We know the importance of maintaining family ties in that is good for emotional well-being. This is why difficult family relations can have such a detrimental effect on psychological and emotional wellbeing. You may then, therefore, consider how your relationship with your daughters is or will effect their wellbeing.
You may, therefore, consider allowing them to also have minimal contact with them too. It may be that they good Islamic behavior in front of them may inspire them to follow the Deen again, especially since they are younger.
Obviously, you would need to be careful that the girls don’t say or do anything that might cause the boys to question their own Deen. Your concerns about this are understandable having already seen your 2 girls go astray.
Perhaps you may just organize a family gathering once a month or so. This way you will maintain ties with minimal risk of negative influence from the girls, especially since the boys will be with you so you can be sure that they are not being negatively influenced by them and all contact between them is positive.
In such gatherings you might begin by not being forceful about Islam, simply letting the girls feel like a positive part of the family unit whilst indirectly seeing how happy Islam is making you all and the positive impact it’s had in your characters. Once the test is strengthened, you will be in a better position to be more direct in your approach to guiding them back to Islam and they will be more receptive to you. Furthermore, this will provide a healthy and nurturing environment for your boys.
May Allah reward your desire to raise your children on the straight path. May He guide you all aright.