Sure, although I'm not exactly sure what you mean (though I could be looking into this too much ;)). So, I think you want either of these:
- You're playing in survival, you want to hop into creative mode but because you disabled cheat codes this no longer works.
- You're playing in a creative world and everyone who joins your world will therefor also start in creative mode. But... you started a creative wold to build an adventure map. So how do you now get new players into adventure mode?
If I got it wrong then please let me know. Either way: both problems can be solved.
#1 From survival to creative, no cheat codes.It's actually really simple: pause your game, click "Open to LAN" and be sure to enable cheat codes. Now you can fully use cheat codes to do whatever you like. But only during this session; as soon as you quit your game and then start it again later the cheat codes will also be turned off again. BUT.. your gamemode obviously retains (stays the same).
This is actually the best way (in my opinion) to set up an adventure world. Start in adventure mode, open to LAN, enable cheat codes and go into creative. But everyone else who eventually will try your world will start in adventure mode.
#2 From creative to adventureThis is also easily doable but you're going to need command blocks. Also: get yourself a compass because you're for this to work you need to place these command blocks in the so called spawn chunks, you can find these in the world spawn which is what the compass is always pointing to. The reason for this is because this area will always remain active, even if there are no players around whereas a normal section in the world will eventually get unloaded after players leave it.
Place a repeating command block which is always active:
- gamemode survival @a[gamemode=!survival,name=!TheBigerGamer]
This would ensure that every player that starts your world will be placed into survival mode unless they're also playing in survival (this can reduce gamecycles). It also wouldn't affect you so that you can continue working on the world if you have to.
Hope this can help!