There should be no problem taking your insulin and diabetes paraphernalia on the plane.
It is recommended to have a letter from your doctor. In nearly 15 years, flying about 8 times a year, I have only been asked for the letter once but I wouldn't risk have the stuff that keeps me alive taken away.
I always take twice as much of everything than I need: twice as much insulin, needles, lancets, test strips, hypo treatment (but not liquids like Lucozade) and, if you have them spare needles.
I highly recommend ensuring you check your travel insurance covers diabetes - it is the thing that is most likely to go wrong.
And, most importantly, have a great time.