I have been advised that give both calpol and Neurofen for high temp like that, it’s was the only way my daughter’s temp went down last week! As long obvs you keep to the 4hrs gap for calpol and 6hrs for Neurofen. I also used a cold flannel which helped bring it down. My lg ended up with antibiotics for a chest infection which helped straight away. Good luck I hope he gets better soon! To answer your question I think I would go if my lo woke up better and had a good night.
Honestly I would still fly... I hope he feels better but like you said you can't go any other time x