Student or Learner
"I no longer need them and I am keen/willing to let go to anyone who needs them." > Is this sentence appropriate? for example if I have some items (shoes/toys...) and I want to sell them to anyone who would like to have them.
"Keen" means you are eager to do it. It's your desire, your hope.
"Willing" means you find it acceptable to do it.
If you say "let them go" it could imply you mean they will be free.
All of this seems unnecessary. If you have items for sale, then obviously you are willing to sell them.
I don't care if you loved them, hated them, needed them once, never needed them but used them when your mother was watching, don't need them now, etc.. All I care about is that they are used but (I hope) in good condition.
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.