Plain old dried banana's are actually pretty good and easy to eat . However quite high in fibre so be carefull after 10 or so.
I really like these things we'ver got here called "fruit bars" which are really tasty. Concentrated Sweet real fruit centres covered in a soft biscuit crust(vege oil, sugar and flour), lightly toasted. Bit of fat and protein, but mostly sugar. Actually pretty close to sports bars in terms of composition, but a third the price. Digest great and are a quick energy boost without the lag of a typical oat based homemade muesli bar.
So think you could be onto something with the ground up cereals
Just have to make it so its not too sticky somehow. Good luck!