Any chance you can change that breakfast to rolled oats? If not then maybe weatbix? I used to work for Kellogg and from memory all their breakfast cereals were low nutritional value and overweight sugar and salt. Like JMan says, I'd watch out for Potato salads or anything with a lot of mayo in them like that.
Just a thought...
As for the Nanna Bingo Arms, try doing bench dips. You can do these in your bedroom by getting a nice stable chair, sit on it then put your feet on the bed so they just reach. Then hold onto the front of the chair with your hands beside you then walk your feet forward further onto the mattress and then try and do some dips. Again, google will show you the form if you need it.
Nanna bingo arms is mostly flabby triceps so anything to work the tris would be good. Pushups is more chest than tris but will help. Squats for quadraceps and situps for abdominals. Some stiff leg deadlifts with bodyweight only is also a good idea. Down to you touch the ground in front, then all the way back up trying to keep your legs straight. If its too easy go with a light weight like a bag of rice or potatos.
Cheers,
Mike