Alex, you have a terrific "travel kit" in your possession! All of those lenses are pretty darn lightweight and make great travel companions... especially in an environment where lots of people might be pressing in on you, something might get knocked about a bit, etc. None of those lenses are made of gold, so to speak, so not too big a concern for an occasional bump or rap, I shouldn't think.
If I were in your position, I would leave the flash behind. Use the built-in flash for the occasional modest fill-flash purposes (portraits of family). As for lenses, I'd be tempted to bring them all (If I had a bag that fit them all AND wasn't too big or cumbersome to carry). However, considering the lenses you currently own, If I could only bring:
One Lens: 18-55 (versatile, lightweigh, 'good enough' quality)
Two Lenses: 18-55 + 50mm (added low-light/indoor + higher quality portrait)
I would expect the longer focal lengths beyond 55mm to be of more limited value to you, while visiting the parks. If you had room for the 55-200, then great.. otherwise, I wouldn't lose sleep over leaving it behind.
I traveled in the parks last year with only the kit lens. The lightweight + 18mm made for a great companion on my 300D, making it pretty darn convenient and super lightweight to tote around all day in the hot sun. I did bring a camera bag.. I have a lowepro that is a shoulder bag but with a contoured bag and a waist strap to keep it securely against your body.. this is a great feature that eliminates the nagging tendency of a shoulder bag to slip down your shoulder all day long. The waist strap keeps everything in place and makes it much easier to wade thru a crowd without concern for having the bag knocked off your shoulder.
At any rate.. the bag is also handy for carrying a spare battery, CF cards, lens cleaning cloth, and to stow the camera while hopping on a ride (especially something like Splash Mountain) or avoiding those brief showers/downpours. My camera and I never had to part ways.. it took all the rides with me and it was never a bother to have it in tow. We also brought my wife's A70 which would occasionally hitch a ride in the bag during rides, lunchtime, etc.
icmp
We will stay for a few days in Florida's Disney World. It is going
to be the first time visit for me and my kids. I dont think I will
be able to carry all lenses all the time, so I will leave the photo
bag at the hotel.
I have:
- 18-55 (kit lens)
- 50mm 1.8 II
- 55-200/4.5 II
1. Should I stick with kit lens or take 55-200?
2. Should I take flash 580EX with me?
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Thanks,
Alex