As-Salam-u-Alaikum I want to know is it haram if I wear a light makeup when going to family gathering ( that’s all women) haram or not
سلام علیکم و رحمة الله و برکاته،
Wearing makeup in front of strangers is haram, whether they are among our family (like cousins) or not. However, determining the antitypes of a makeup depend on the person and on the society and the situation. For example, dressing in colors may be assumed as makeup in a society, while it is not in another, or using colorful eye lens might seem make up to some people but may not seem makeup to others, especially if in a society people usually have colorful eyes, even some cosmetic surgery may seem makeup to some but may not be makeup to some others, and wearing marriage ring is another example that can make contraversy.
Thus simply saying, your question has no strict yes/no answer, as it depends on many things. You yourself should decide if the what you call light makeup should be considered as makeup or not. Some scholars sometimes count a number of antitypes that can be considered as "allowed" in some common situations in a society, maybe you can consult with a scholar then.
Edit. Sorry I had not read your question carefully that you have already written all the participants in that family gathering are woman, so why bother at all? Women are Mahram to Women, at least as long as both are Muslim:
وَقُل لِّلْمُؤْمِنَاتِ ... لَا يُبْدِينَ زِينَتَهُنَّ إِلَّا مَا ظَهَرَ مِنْهَا ۖ وَلْيَضْرِبْنَ بِخُمُرِهِنَّ عَلَىٰ جُيُوبِهِنَّ ۖ وَلَا يُبْدِينَ زِينَتَهُنَّ إِلَّا لِبُعُولَتِهِنَّ أَوْ آبَائِهِنَّ أَوْ آبَاءِ بُعُولَتِهِنَّ أَوْ أَبْنَائِهِنَّ أَوْ أَبْنَاءِ بُعُولَتِهِنَّ أَوْ إِخْوَانِهِنَّ أَوْ بَنِي إِخْوَانِهِنَّ أَوْ بَنِي أَخَوَاتِهِنَّ أَوْ نِسَائِهِنَّ ...