Ike did the right thing in resisting French and British efforts to maintain their former clout. Their claim was an unjust one and the war was a stitch-up. It's easy to say things were wrong when we look back, but hindsight is 20/20. I for one still think he was one of the best Presidents in history (Admittedly, I'm an external observer).
The British and French leadership on the other hand was about as principalled as a sack of stoats. Nasser was crazy and fanatical, but Egypt's claim was a more honourable one. The history of Anglo-French dealings with Egypt over the canal prior to 56 is one of treachery, duress, bribery, corruption and shortsighted greed.As ye sow, so shall ye reap.
How was their claim unjust? I admit with the lease expiring in 1966, and no liklihood that Egypt would renew it, it might not have been worth the effort. It's my understanding from secondary sources in his later years Ike acknowledged this as an error, as did Nixon. They thought they'd bring Egypt and the Arab world into the fold, it didn't work. Either way, I wouldn't look at this as particularly damaging to Ike's reputation.