What is the ruling on not fulfilling a vow?
A vow is a commitment towards Allah, The Almighty, and so, it should be observed as much as possible, and it is impermissible to take it lightly. Allah, The Exalted, Says –in commending the believers (What means): "(Because) they perform the vow and fear a day whereof the evil is wide-spreading." [Al-Insan/7].
We collect funds from mosques and other sources, saying: "For the poor, the needy, widows, orphans, and those who do not beg insistently." After paying the stipends of the families registered with the Zakat Committee, an amount exceeding 6,000 dinars remained. Is it permissible for me to save it for upcoming months when I may not be able to collect the stipends?
These funds are received by the committee as representatives of the zakat payers to deliver zakat to those entitled to it. It is well-known that delaying zakat while being able to pay it is not permissible. Imam Al-Nawawi (may Allah have mercy on him) said: "Zakat must be paid immediately if one is able to do so, by the presence of wealth and the eligible categories." [Al-Minhaj] Therefore, the committee must distribute the zakat to the eligible recipients without installment payments or using it to purchase material goods for them, as the committee does not have authority over the poor to allocate it in this way. And Allah Knows Best.
Is it permissible to pay the expiation of an oath to a charitable party as it feeds the poor and needy such as Tkiyet Um Ali?
There is no harm on authorizing someone to handle the expiation of another to the poor and needy, since Shafiee's jurists stated that authorizing someone for the purpose of distributing Zakah, expiation and vow is permissible as stated in [Mughni Al-Muhtajj,vol.3/pp.237]. At last, the intention of the person who intends to authorize someone else suffices in this regard. And Allah Knows Best.
Is it permissible for the guardian to give Sadaqa (voluntary charity) from the money of the orphans?
It is impermissible for the guardian to donate from the money of the orphans because he is entrusted with the safekeeping of that money, and is prohibited from donating it.