Can a couple who have undergone sharanagati, celebrate Shasthiabdapoorthi? What will be a suitable method to perform Shasthiabdapoorthi? We live in a Divya Desam; as it is a village, temples for demi-gods exist here. We are asked to donate to fund these temples; can we contribute as a Bhagavad Aradhanam? Some do not understand this concept. We belong to the Vadakalai sect. The temple here follows the Thenkalai tradition and demi-gods are available in this temple. Can we go to such temples?

Couples who have undergone sharanagati can certainly perform Shasthiabdapoorthi; this is mentioned in the Sutra-s. The method to perform Shasthiabdapoorthi includes chanting of Vedas, erecting Kumbham, etc. There are no specific rules around this. Srivaishnava priests know what needs to be done and one can engage them for such functions. Importantly, Acharya sambhavanai, blessings with akshatai, Tirumangalya Dharanam, Aupasanam, etc. are a must.
As the temple village might have sanctums for demi-gods, it will be awkward when asked for a donation for their kainkaryam and one might not have a choice and have to oblige for the sake of harmonious living with the society. It appears it would be better to adjust to situations, instead of trying to determine whether these are allowed by scriptures. We are making many unwanted and unjustified expenses such as cable TV subscriptions, etc. Such donations can be treated as one of many unwanted expenses. If possible, avoid these expenses. If there are demi-gods in temples, ignore those sanctums and worship only at Perumal sanctums.