If my mother-in-law shraddha happens to fall on Dwadasi, can we do paranai? Paranai time is in the morning and the time for shraddha is after 11 AM; how to observe paranai?

Karta and other Swami-s who participate in the rituals must not do paranai in the morning; others can do paranai. Since one whose father is not alive must not partake twice during daytime, they will not be able to partake ishta pankti; if one needs to partake ishta pankti, one can do paranai by drinking water.