My son/heir wants to join the Varangian Guard, should I let him?

I'm currently fighting to try to subjugate Ostlandet, and my son/heir prompted this message:

My current king (Jarl Tolir) is 56 years old, and I expect him to die at any moment. I just had a successful revolt for independence against the Queen of Sweeden, so I had to push his Ambition to become the King of Norway as soon as possible. I have another son, but he's a chaste-craven-homosexual (which is not heir material). If Hrane goes off to join the Varangian Guard will I lose him forever, or will he return when my current king dies?

Should I allow my only good heir to join the Varangian Guard?

Upon playing further, Tolir took until the ripe old age of 77 to pass. Hrane (now 48) has returned to claim the throne of Norway, along with a pleasant surprise:

Hrane now has a nice starting prestige of 279 (+200) and a bump of the royal coffers by 200 as well. Be aware, I was prompted that being a member of the Varangian Guard is dangerous, so I'm assuming that members are more likely to die than if they were sitting in a court. However, if you have more than one valid heir (even a chaste-craven-homosexual backup), I would recommend sending your sons to the Guard if they ask.

Yes, you should let your sons join the Varangian Guard. If they return safely, they bring +200 gold/ prestige when they return for their claims and the "Varangian" trait (+2 Martial, +1 Diplomacy).

No. Your heir could come back blind and castrated, amongst other outcomes.