Is it permissible for us to make the call to prayer (adhan) or should we suffice with just the iqamah when establishing congregational prayer at home a long time after the prayer's prescribed time has begun?

You must call the Adhan (definition) for the prayers you gather to perform, because it was legislated to manifest the rituals of Islam, to announce the entry of the prayer time, and to call people to the congregation. It is a confirmed Sunnah (definition) for every group, especially if there is no other mosque nearby where the Adhan is called. The Adhan is particularly required of you as you are in a country where Muslims need to preserve the outward rituals of Islam. Your prayer is valid even if you pray without the Adhan, but by doing so, you are doing wrong.