As an adult with work responsibilities, it will be hard to match the energy of your boys and their desire for imaginary adventure. This brings me to mapping, two very time consuming matters when it comes to fantasy world building. Typically the moderator or game master makes a map of a world, the characters place themselves in it and he suggests adventures and they began building their map of the world.

I suggest a realistic look at medieval life, from the local perspective, where nothing is known other than the village, the nearest keep, village or monastery and the very limited topography in between. Let your sons make a map of the world and invest it with the fancies they will, and then, as they act out and play their journey, you can fill in the actual facts—“No, this is not an Elvin wood, but there is an ancient image carved at the knee of a massive tree…”

Some randomized encounter tools will help you entice your boys through their adventures and fill in the vast gaps in their imaginary map.

Travel Encounters

Having the players roll for their travel encounters with you interpreting them will spread the burden of play and give them more dice time, which is beloved by gamers. Many tables of your own devise for towns, villages, cities can be made. If one wishes to have dungeon adventures than the same basic 36 point curve using 2 dice can be used for tables for direction, something like this one, but customized for different types of ruins such as ancient cities, castles, necropolis, etc.

Passage

To check for variations of a result roll one die.

2 Trap, collapse, structural danger

3 ladder

4 stair

5 ramp, bridge, gradual rise 4-6 or decline 1-3

6-8 Continues

9 Door or passage left 1-3 or right 4-6

10 Doors or passages left & right 1-4 or left, right & ahead 5-6

11 Guardian, sentinel, prowler or stalker encounter

12 Dead end

Chamber

2 Cell of a prisoner, malevolent 1-2, needful 3-4, benevolent 5-6

3 Egress via, door, stairs, passage, hatch, latter…

4 Deeper access via, door, stairs, passage, hatch, latter…

5 Servant 1-2, guard 3-4, or pet’s 5-6 quarters

6-8 No egress, roll on relics table 1-3, empty 4-6

9 Kitchen, hall, throne, library, chapel, crypt, smithy, laboratory, observatory, barracks, temple, altar, armory, stable, torture chamber…

10 Quarters of a personage, past or present

11 Storage: trash 1, dead 2, goods 3, foodstuffs 4, weapons 5, trove 6

12 Lair of a fiend 1-2, monster 3-4 or holy presence 5-6

Wilderness

2 Human encounter, treating serf results as corpses or bones

3 A prowling beast or monster

4 A clue or a path

5 Change of habitat and/or terrain towards it opposite

6-8 Monotony

9 Change of habitat and/or terrain to a greater extreme of same type

10 Passive animal life

11 A lair—animal, monster or villain

12 A relic or ruin

Habitat Type

Roll the number on the right or higher with one die for a human encounter

2 Fresh water [6]

3 Bog, marsh, swamp [6]

4 Lush forest [6]

5 Forest [6]

6 Wood [5]

7 Mixed wood and pasture [5]

8 pasture [4]

9 Heather, moorland [5]

10 scrub [6]

11 Desert, waste barrens [6]

12 Salt Water [6]

Terrain Features

1 Depression, crevice, pits

2 Ancient ruins

3 Flat

4 Flat

5 Flat

6 Gently rolling

7 Uneven ground, broken

8 Rising

9 Prominent hills

10 Mountain [walkable]

11 Mountain [scalable]

12 Mountain [unscalable]

Human Encounters

2 A helpful individual

3 Indigenous observers

4 An individual in need

5 A pilgrim, merchant or workmen band

6-8 Local serfs

9 Local military

10 Highwaymen, raiders, pirates, bandits

11 A duplicitous individual

12 A fiend, sorcerer, witch, etc.

Relics

2 Monstrous bones

3 Human bones

4 Garment, cap, cowl, blanket

5 Common coin, tool, arrowhead, etc.

6 Broken tool

7 Fire pit, ashes, stake

8 Broken weapon

9 Broken/rusted armor, helmet, shield

10 Lost Weapon, tool, armor

11 Cached valuable, map, religious relic

12 Item of epic interest, such as a magic ring, sword in a stone, etc.