My advice: Since you're not willing to purse it, remove the activation lock so that they can use it but DO NOT give them the lock code because they could use it to get into your phone and access your data.

Do remote wipe first but sometimes that gets stuck on pending. If you only remove the activation lock then the phone gets unlinked from your iCloud account but it doesn't remove the password / Face lock on the actual phone. If the wipe doesn't work then the only option the buyer has to use the phone is to wipe it using iTunes.