we r planning to make umrah with our 2 kids 4 years / six months (by then). doctors and other people advise against because of the children (risk heat/diseases). what mentions islamic tradidtion?

There is no Hadith with regards to whether you should travel in this condition or not. This is a decision that you as the responsible person of the family have to make. You state that the doctors advice is not to travel with the kids. Surely, there must be some reason for them to suggest this. You should make Istikhara and finalize your decision. Once you make your decision remain firm upon that and then do not allow Shaytaan to whispers doubts into your mind. Thereafter what will happen is upon the command of Allah and you should accept that wholeheartedly. However, due consideration has to be given to advice that is given on sound grounds and have merit therein.

And Allah Knows Best

Muhammed Zakariyya Desai