So I refrained from posting this since I noticed it was briefly mentioned by plasmascreen, but since I’ve made two other posts on this thread that isn’t solely related to your topic, I guess I’ll expand on it.
Everyone loves a reward, don’t they? I don’t know about you, but I sure do! Acknowledging a player’s effort by giving rewards would be a good idea as it gives them both a sense of satisfaction (they’ve gotten something), a sense of achievement (they’ve learnt something) and a method to brag to their friends!
Adding something like medallions that are publicly visible to everyone on the server to show how well people are doing on your game would support the above, then adding something like a currency that people gain through little minigames and parkours, etc (possibly even an optional tour around the map? I know that Cadbury World gives those who go around the site free chocolate), then allowing them to spend said currency in a store for things that they might find fun, from catalog gears (allowing them to experience what they might not be able to afford) from your own custom perks! If you really wanted to profit off it, you could also add a way for people to purchase them, but I wouldn’t advise this in the sense of gameplay, as it would discourage people to play and learn and encourage them to just spend money.
You could add medallions or badges (or anything else) for every area, with a way to view your current ones and how many you have missing, whilst currency could be given for completing minor things in an area and the actual reward once they complete the entire section. Other players could be able to view what you have and don’t have via a custom player list where you click their username or profile picture to bring up the respective UIs. A possible restriction to certain areas that you can’t access until your complete a prior area, and having to utilise what you’ve learned previously to complete that area will help add to their sense of achievement (they’re able to apply what they’ve learnt, they’ve earned something new) and, personally, as a player in those kind of settings, I’d strive to have every single thing available (that’s free), which in this scenario would be to unlock all the areas, thus promoting people to actually play the parts of your game and learn from them, allowing them to go back and revise what they’ve learnt later on as well, in case they’re unable to apply their knowledge. Adding things like hints would be a good idea so that they don’t just get stuck the moment they run into a stump that they can’t get past. There are lots of things you could do and add to improve the gameplay and player’s immersion into your game, from Camera Cutscenes to dialogue (not monologue, let the players reply! That’ll make them feel more involved in your game).
Hope this helps. 
EDIT: As a person, I love to read. This is mainly due to the fact that I’m able to envision scenes that wouldn’t normally be applicable in this world, or to me at least. From flying through the sky in fantasy settings, to even the most cliché of romance novels. You could try and incorporate things like that - referencing books in some way, whether within your game (your own books) or outside of your game (books written by authors) could also promote reading, for example one of the previous egg hunts, which was based in a library.
Extensive monologue or dialogue between NPCs will often bore your younger audience, which is where allowing your own players to be able to “converse” (through fixed choices) to your NPCs would make it feel less dull, with maybe something abrupt happening between dialogues, causing you to go into an event? Maybe even make it so it’s like a “pick your path” kind of book, where rather than one correct path, you can have your choices impact (whether largely or not) your experience within the game, such as having a solo boss battle vs gaining an ally to fight the boss, which would promote people to think more about their decisions in life and not act so whimsically.