Lenya
“Then use your bows, as long as the situation allows for them. And swords for the other situations.”
If one of them (Det preferably) is strong enough to use the mighty composite longbow, he should use that one.
Routine orders for the two mercs are to protect Belaver (Kef) and Lenya (Det), if necessary, otherwise support the melee fighters by attacking annoying minions or dangerous targets engaged by them. The mercs should not open combat on their own, unless they are told so.