Answer
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
1- If there is an urgent need to build or renovate the mosque, then you should donate the costs of Hajj to the building of the mosque.
2- If there is no urgent need to spend the cost of a voluntary Hajj on renovating the mosque, then performing Hajj on behalf of parents is better.
Answering your question, the late Saudi scholar, Sheikh Ibn Baz (may Allah have mercy on him) stated:
If there is an urgent need to build or renovate the mosque, then you should donate the costs of Hajj to the building of the mosque. This is because of the great and ongoing benefit of doing that. And it will be helping the Muslims to establish prayers in congregation.
But if there is no urgent need to spend the cost of a voluntary Hajj on renovating the mosque, because there are other people who can contribute to the renovations, then performing Hajj on behalf of parents, either yourself or through a trustworthy proxy, is better.
But it cannot be done on behalf of both of them in a single Hajj; rather you should do Hajj on behalf of each of them separately. (Majmou` Fatawa Ibn Baz, 16:372)
Almighty Allah knows best.
Source: www.islamqa.info