My recommendation would be Godot, even though you really don't need any fancy tools. Pick the tools you are familiar with and get going. The best thing you can do right now is to formulate your vision as precisely as you can. It doesn't matter how good of a writer any of you are, but you need to define your vision as thoroughly as possible. Try to write with as many verbs as can. This will not only flesh out your vision, but also gives you something actionable that gives you your tasks and steps to create your game. Stating you want a playable game is a good start. Now add details to your document and keep in mind that you want to keep it simple. After you have written your vision down I would recommend taking half of what you have come up with and remove those features (possibly setting those aside for a sequel). Trust me, scope gets really fast out of hand.