Minecraft – How to place waypoints on your map in MInecraft PE

Simple Mob Grinder

The simplest mob grinder you can do is to use gravity to kill off the mobs.

Build a really tall hollow tower out of cobblestones with no windows. Make sure the hollow shaft is 2x2 wide so there is enough space for spiders to fall down as well as any other mobs. Make sure this shaft is built over something solid - stone, not sand, dirt or gravel. The reason this is all dark is so that the mobs will still spawn during the day as well as at night.

At the top of this tower create a large room, again with no windows. Something around 15x15 will do. Make it about 5 blocks high and keep a hole in the floor over the shaft so that you have a big dark room with a shaft in the middle. In theory the mobs will spawn in this big room, wander around and fall down the shaft, splatting on the ground and leaving a load of goodies for you to sweep up. Don't forget to add a door at the bottom of the shaft so you can get in there and grab it all.

Really that should be all you need. You can expand this idea however you fancy; underground grinders, multi-room grinders... however adventurous you want to go. Bear in mind though that Mobs will only spawn when you are near to them, so you should build a house near to your grinder, or at least hang around near it when you want to get stuff.

I assume that by "world" you mean a specific location in the world, the main base/house probably.

Pocket Edition worlds aren't terribly large so any place with distinctive above-ground features or nearby landmarks should be fairly easy to find by flying around. Searching the whole world in flight should only be a matter of minutes.

Failing that your son might consider killing himself (in the game). That would cause him to respawn at the last bed he slept in if it is intact or at the initial spawn, might be easier to find his base from there. If he has gathered any resources that he would hate to lose he could place a chest to stash them in and put up a marker to find it easily (a tower of cobblestone with torches high on it is simple and effective for that). Building a similar beacon close to home can help prevent getting lost in the future.