Vaikasi Visakam is said to be the day when Lord Muruga/Subramanya incarnated in this world with the mission of saving earth from demons like Soorapadman.
Aadi Krithigai is a day auspicious for Lord Muruga. This year it falls on July 20. Karthikeya or Muruga is the second son of Lord Shiva and Mother Parvathi. Interesting and inspiring are his birth and feats, which are elaborately described in the Skanda Purana.
In the pooja room do not place pictures of Gods along with pictures of departed souls like grandfathers, great grandfathers etc. You can place them in the pooja room on a different side. For eg., if Gods are placed facing east you can place the pictures of the deceased facing south or north etc., If you worship this way then the blessings you will receive will be several fold.
Lighting of lamps with threads made from cotton will maintain harmony in the family.