For whom the arrangement of iftar is made in the mosque and why it is done? Do locals do iftar or the travellers? If only they are locals then what is the need of collection? Each one can carry iftar from his home and if there is no fear of missing jamah then each one should do iftar at his home. It is not lawful to collect money from those whose full earnings or more than half is of interest. If you know that the iftar is arranged with the interest money, you should avoid attending such iftar.
Allah (Subhana Wa Ta’ala) knows Best
Darul Uloom Deoband