Allah's Messenger (saws) said: ‘When a man dies, his deeds come to an end, but three:
1. recurring charity,
2. or knowledge (by which people) benefit,
3. or a pious off-spring, who prays for him (for the deceased).’
Sahih Muslim, Book 013, Number 4005, narrated by Abu Hurayrah
One out of the three is doable, writing it is then.