Holiday and shuttle launch advice

Im going to Florida for my holidays in May and there are a couple of launches planned for the time im over ( one at midday and one at 7pm).

I had thought about just taking my P&S (A790IS) but im wondering if it is worth taking the 400D with me.

The problem is that the carry on baggage allowance for the flight is about 7kg and im thinking that my bag may be close to it (400d + sigma 18-50 f2.8 + sigma 70-300 APO + grip +batteries +flash).

Anyone with experience of shuttle launches got any tips as well?

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My guess from what I've seen here is that 300mm won't be long enough & the launches won't be even close to on the scheduled time. Good luck!