Let's see, I think that Freddy would have a lazy but 'gets work done' when needed son, who would be a Cavalier. Vaike would have a smart and slightly 'proud' (like Vaike, but not as extreme) daughter, who would be a Thief, but she doesn't like fighting that much. Stahl would have a kid who eats a little less than the average person, and is in general an anything but average son, who would be a Mercenary. (If Sully's kid is different, then so is Stahl's.) Kellam would have a somewhat popular and religious kid, and he became religious when some 'divine intervention' saved him from death, but he later found out that it was his dad. He would be a Priest. Lon'qu would have a shy-from-girls daughter, who is also popular with the guys, especially Freddy's son (because whatever), and she would be a Wyvern Rider.
Donnel would have a hard-working son who is a bit too serious about things than what he should be. He would be a Fighter.
Ricken would have an above-average height daughter, who is scared off animals of any kind, and prefers to just help out around the camp or read. She would be a Mage.
Gaius would have an anti-sweet eating son, after getting a cavity at a really young age. He would also be easily noticeable, due to wearing a necklace of the tooth that had the cavity, as a reminder. He also dislikes thievery, and thinks his dad should become something more respectable. He would be a Myrmidon.
Gregor would have a daughter who is gifted in the art of speaking, being able to learn languages easily, and can speak them well. She also gets mistaken to be younger than what she appears, except for her mature voice. She would be a Troubadour.
Libra would have a daughter who looks very much like him, and is commonly mistaken as his younger sister. She snaps at people for not noticing that Libra is male, saying that it's 'obvious', and get's constantly told by Libra to not be so rude. She thinks that her dad is disappointed by her natural affinity for dark magic, and not staves.
Henry's son would be a well mannered kid, but is prone to pulling 'pranks' on people, but he actually just scares them. He gets a bit sick to the stomach by seeing his dad's love for blood and gore. He also dislikes Henry's jokes, but he doesn't want his dad to find out. He's a Barbarian.
I probably thought these out a bit too much, and they probably seem weird, but eh.