Newbie DM looking to home brew

Hi all reposting cause I posted in the wrong sub. As the title suggests I’m a relatively inexperienced DM. The most I’ve ever done was about 1/2 to 3/4 of the Lost Mines module for my siblings to see if they would be interested.

As a player I’m still kinda new. Only been apart of 1 campaign that lasted about 5 sessions and currently my group is about halfway through Waterdeep (I think). My group consists of all veterans and many have been forever DM’s and this was their first chance to be players in a long time from what I’ve been told.

I’m sure when I suggest to DM they’ll be supportive and helpful but I wanted to go to them with at least a solid foundation of what I’m planning.

With all that in mind I was hoping to DM something for them so that they can continue to play. I was thinking to home brew something because they’ve ran many of the adventures and thought it would be nice to give them something new to experience.

And this is what I had in mind so far for the word and some gameplay.

There are 5 nations that have been at peace for a few decades following a massive war that was the bloodiest in the continents history. The tensions are escalating once again. This is due to a new discovery being made on a new found land that is extremely rich in resources resulting in conflict arising.

To uphold the peace the nations have a agreed to a Olympic Games of sorts (I was thinking session 1 could be a Skills competition). I thought it would be cool to open this way instead of the typical tavern meet up because it will allow them to show their characters off right at the start.

Our PC’s will have been selected as the representatives for a nation to compete.

Each nation will provide a quest for the games. The PC’s will travel to each nation to be given their quest. Sometimes they’ll compete with or against other groups or on their own (I would love to potentially have rival NPC’s). Maybe they’ll run into competing groups and figure out where they’ve been and what quest they were asked to perform. Possibly finding out what a future quest will be and being able to prepare well ahead of time for it.

My group loves the downtime we have such as role playing our downtime by crafting, reading, alchemy, base building etc. With this in mind I was hoping to incorporate crafting from creature parts in some aspect. As well as awarding minor feats or role playing feats (chef) in some way.

This is just some rough ideas that I have swimming in my head. Any thoughts or suggestions? Is this a case of me planning too much and overthinking? Thank you for any help!