How to allow certain commands to non-admins?

I run a modded server based on Pixelmon, and one of the mod's command is /checkspawns which is to display to the player the Pokemon spawn rate at the location they typed it.

Unfortunately, this command is only available to OPs, or admins, but I want every player to access this command. My question is this:

How do I allow a command exception to non-admins?

1) without giving them access to other commands

2) that works even for mod commands and not just those from vanilla

Quote from Julian

Install the mod forge to bukkit permissions and the plugin Luckperms (using magma)

i think you meant PermissionsBukkit because I cannot find BukkitPermissions in the magma plugin library.

the only thing I did was add the Luckperms plugin. I tried adding the node "pixelmon.command.checkspawns" in the Luckperms editor but it didn't work live in the server. What do I need to do with BukkitPermissions?

do every player in my server need to download ForgeEssentials into their mod folder as well? How can I tell if they do or don't?

update: players don't need to download ForgeEssentials for themselves to join the server.

Every commands in the Pixelmon commands list works in ForgeEssentials EXCEPT for /checkspawns. By default it says "You do not have permission to use this command" but after allowing the /checkspawns node, it changes to "You must be an OP or have permission to perform this action." for the members of the group I created.

Using ForgeEssentials

1) "/p group gName create" <---------------------------------- made a group, let's call it gName

2) added members in the group

3) "/p group gName allow command.givemoney" <------ works

4) "/p group gName allow command.checkspawns" <-- doesn't work

The message "You must be an OP or have permission to perform this action." persists even after I allowed the following nodes.

1) pixelmon.command.checkspawns

2) pixelmon.command.checkspawns.normal

3) command.checkspawns.normal

4) pixelmon.checkspawns.normal

It seems like there's an extra layer of security, probably made by the Pixelmon mod, because even after putting someone other than myself into the _OPS_ group (already-created group of ForgeEssentials), they can do every command like /gamemode 1 and commands in Pixelmon EXCEPT /checkspawns because oddly enough, it still says "You must be an OP or have permission to perform this action."