Firstly, I hope that this thread is in the correct place.
I am hoping that there are enough people out there that can help me with this one. It's mostly in relation to exposure and ambience. I have been asked to be the photographer for my cousins forthcoming wedding, which I really did not want to do and declined many times at first, but agreed on the day that they laid her mother, my aunt, to rest. I have been lucky enough to have captured some good enough pictures of events in the past, which is why she asked me to do this. The problem is, I want this to be right for her, I want to be able to capture the ambience of the first dance, which I know is going to be low light, without it looking brighter/lighter than it actually is, and I want to be able to capture the detail in the white dress without blowing it out. The kit I have is:-
Canon 550D.
EF-S 18-55mm f/3.5-5.6 IS.
EF-S 55-250mm f/4-5.6 IS
EF 50mm f/1.4 USM
EF 85mm f/1.8 USM
At the moment I do not have a Speedlight, but thats because I am in two minds about buying a bunch of Nikon kit as follows:-
Nikon D90
AF-S DX 18-200mm f/3.5-5.6G ED VR II
AF-S DX 35mm f/1.8G
AF-S 50mm f/1.4G
SB-900 Speedlight
Any advice on how to take a pic of the dress without blow outs, and on the happy couple in low light while maintaining the low light atmosphere would be greatly appreciated, as would any other helpful tips.
Many thanks in advance

I am hoping that there are enough people out there that can help me with this one. It's mostly in relation to exposure and ambience. I have been asked to be the photographer for my cousins forthcoming wedding, which I really did not want to do and declined many times at first, but agreed on the day that they laid her mother, my aunt, to rest. I have been lucky enough to have captured some good enough pictures of events in the past, which is why she asked me to do this. The problem is, I want this to be right for her, I want to be able to capture the ambience of the first dance, which I know is going to be low light, without it looking brighter/lighter than it actually is, and I want to be able to capture the detail in the white dress without blowing it out. The kit I have is:-Canon 550D.
EF-S 18-55mm f/3.5-5.6 IS.
EF-S 55-250mm f/4-5.6 IS
EF 50mm f/1.4 USM
EF 85mm f/1.8 USM
At the moment I do not have a Speedlight, but thats because I am in two minds about buying a bunch of Nikon kit as follows:-
Nikon D90
AF-S DX 18-200mm f/3.5-5.6G ED VR II
AF-S DX 35mm f/1.8G
AF-S 50mm f/1.4G
SB-900 Speedlight
Any advice on how to take a pic of the dress without blow outs, and on the happy couple in low light while maintaining the low light atmosphere would be greatly appreciated, as would any other helpful tips.
Many thanks in advance