Wedding Advice
Get someone to assist in organising guests from that list ready for the shots (preferably another guest who knows everyone)
Those two will at least give you a bit of breathing space and help you concentrate on your photography
You also have to make yourself heard, when a group is arranged for the shot make them aware they should be looking at you and your camera and not Auntie Mabels or the Bridesmaids friends.
Leave the 100 and 50 at home, the 18-135 will suffice and changing lenses is one less thing to worry about.
EDIT: make that leave the 100 and 50 in the bag but forget them (just in case the worse happens and the 18-135 locks up)
My Names Alan, and I'm a lensaholic.
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If you're not experienced with shooting portraits and couples, "practise" would be a good advice, but if you can't practice enough, try to shoot an engagement session with the couple sometimes before the wedding, if it's possible. Watch a couple of Jerry Ghionis lessons on the web beforehand (but it's easy to get overwhelmed with the info).
Don't point the flash directly at the people, unless you really have to. Use bounced flash as much as possible, bounce it off a white surface preferably. Camera in whatever mode you're comfortable shooting in, flash in P-TTL, 'cause manual flash can be too tough in a quickly-changing environment of the wedding.

I would lower their expectations so you under promise and over deliver.
I wouldn't worry about your 100mm you will need that for the b and g portraits. I would also take the 50mm to ideal for quick shots outside the church.
Good luck and keep smiling it will relax the b and g...
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Currently on a Pentax hiatus until an FF Pentax is released

Keep checking the screen - you may have twiddled something in the heat of the moment.
Get ready to set the camera to daylight settings as you walk out the door. Practice this.
The 100 on about f3.5 will make a lovely portrait or candid lens.
If it's dark and you're not allowed flash, you may need the 50, especially on a K3, but otherwise the zoom will be capable of doing the whole day.
Be ready for the kiss.
Take charge of the confetti line-up, and make the couple walk slowly!! (they will race towards you and it'll be over in a flash)
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I spoke to them, B &G,today, and we are going to arrange to meet up and take some engagement shots.
I appreciate all the advice and am going to be practicing like mad.



I'll also second Cabstars recommendation to lower the couples expectations, make it very clear you are not a professional.
My Names Alan, and I'm a lensaholic.
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If you don't have a diffuser or flash bender for your flash, get one and practice with it.
Good luck.
Pentax K10D + Vivitar 55/2.8 macro + Super Takumar 55/1.8 + SuperMultiCoated Takumar 85/1.8 + SuperMultiCoated Takumar 135/3.5 + SuperMultiCoated Takumar 200/4 + Super Takumar 300/4
Pentax K100D + DA18-55ALII + DA55-300
Pentax K5 + FA31Ltd + M50/1.7 + DFA100WR + M120/2.8 (+ DA18-55WR at occasion)

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caj26
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I have a three legged thing tripod
K3
Metz 48 flash [not so competent with this yet]
18-135 wr lens
100 wr
50 1.8 af
Any suggestions would be appreciated.