hi there,
wedding couple's grandparents (if they are able to go up the steps), parents , siblings (with inlaws and their kids) and bridal entourage (brothers and sisters) normally are on the stage for the toasting (3x yum seng or the 1x cheers) segment.
for the table to table photography, the parents will be present at the tables for their respective friends or family that they know. For your own personal friends and colleagues, both parents may choose not to be present for the photography. (it makes more sense). Sometimes, if your parents visit their friends table, they may just yum seng for the fun of it and the couple don't need to be present. Imagine yourself at 60 years old at your child's wedding and you see your other 50 - 60s year old friends. You have fun with your friends, don't really need to join in though. Unless during the photography of the table to table, one of your dad's friends decide to have a toast, you may decline or just join in to have fun even if you do not know your dad's friend at all. Don't worry too much about it. Just enjoy the wedding!
Hope this helps.
Cheers!
Benny Loy