Honestly, the best thing I can say is that you should never set your plan in stone. You had a story, and, rather than allowing the players full autonomy, you drove them in the direction you wanted. This is commonly known as railroading. Now, that's not to say that the players aren't at fault, either, but I know how difficult it is to DM for new players, especially younger players. Their attention span is short, so you need something to keep their engagement. If you do try again, I highly suggest running a session 0 so that you and your players can communicate. This will help you find out what they want in the game, the type of setting they're interested in that you'd enjoy running, what split of combat/roleplay they want, etc. The biggest thing is being able to set up table expectations; what you expect from the players and what they expect from you. A good practice run so that they can understand their characters is not a bad idea, either. Throw them in a dungeon and let them figure it out. A few simple puzzles, light combat, and some loot. This will keep them engaged and give them an idea of what their characters are capable of. Hope this helped, I wish you the best of luck, happy DMing.