It's possible - I just interpreted the line slightly differerntly - that Squall oblivously insults Laguna throughout the game, and clearly doesn't think much of him when they finally meet. Therefore, Laguna assumes, (mostly likely correctly), that Squall will not be pleased to find out that his father is someone he thinks quite lowly of already. I don't think Squall really gets it.

As for the aging, in the ending FMV, when "young" Laguna's face fades into the "old" Laguna, he clearly now has wrinkles around his eyes and stuff - although the details are slight.