I would continue the antibiotics. There is definitely some ulceration of the skin and if there is some conjunctivitis present then those can be challenging to treat. So antibiotics are definitely going to be an ally, and ceftazidime has few side effects. I am concerned that there may be a significant fungal component as well. The moist looking crusting covering larger areas can be more consistent with fungal, although not always. If it is not starting to clear with antibacterial options especially that worries me for something fungal. The best course of action would be a skin biopsy of one of the abnormal areas, which would be a quick little sample of the full thickness of the skin sent off to the lab to look for bacterial, fungal, and viral components. Then you'll have a much better idea of what you're trying to treat rather than just continuing blindly and hoping for progress. Whatever is affecting the skin can also affect internal organs as well, whether it's fungal or bacterial, which is most likely why he's feeling so crummy. Sun is always great, as is keeping him hydrated. There's nothing wrong with pedialyte but also get just good old water in there too.