first tri this sunday. last minute advice needed

relax and do not overly worry about finishing times.  Just go out there do your best and enjoy yourself. 

Take it easy on the bike.  Save something for the last 1/2 of the run.  Look around and enjoy!

If your level of readiness and shape allows - redline all the way.

Don't get bogged down in the opening chaos of the swim start. STand to side just for a few seconds, then swim your swim with confidence (i'm assuming first time race in open water etc) If you have not done a bike/run brick to prepare for the feel of running off the bike, I would do a short one this week if training/time allow. Feels different. Otherwise, good luck. Report back!

Hang out toward the back of the swim start and take the first 100 yards easy.  Once you feel comfortable and have a good rythmn,  start to increase your effort level till race pace.

#1 is have fun!
#2 set a goal...time to finish, swims all the way without using a buoy or kayak, no walking on run, etc. but it's important to focus on something
#3 HAVE FUN!!

If it makes you feel any better this past Sunday was my first tri also.  I had a blast.  I did better than what I was planning.

To add to this, my wife has decided to enter the race as well.  this will be her second tri.  now i'm worried

Make up a packing list so you're not forgetting anything. Also, don't pack more than absolutely necessary, you have very limited space in the transition area where you need to store everything you bring, have room for your bike, and do you transitions.

It's kind of hard giving advise as to race strategy, not knowing your strengths and weaknesses. So instead, let me give you my strategy (which worked out ok over the weekend, won my AG). I'm a really slow swimmer (I breaststroke the entire distance with my head out of the water, you get the idea) so I stay on the outside and all the way in the back; I'm better off staying out of the mayhem and let the other swimmers get away from me, allowing me to take my time and minimize energy loss. If I go as hard as I can on the swim, I may save 30 sec. in a sprint, but I know that will cost me lots of energy, so I don't. My strengths are the bike and the run (yes, I know... I should stick with duathlons then!), so as soon as I get out of the water, I rip off the wet suit to my waist, remove the cap (not wearing goggles, but if you do, now's the time to remove them). Once I'm at my transition area, I drop my cap and pull down the wet suit to my ankles then I step on the wet suit and rip my feet out. I have a bucket of water that I step in and then step into my shoes (if I'm not using my tri shoes, then I leave them on the bike). Make sure you put your helmet on before unracking the bike! And then on with the race belt that I've attached the number to. After I've run to the mount line, I get on the bike and go moderately hard for the first mile where I take in a gel and drink some water. After that, the bike is an all out effort for me until I'm about 1/2 mile out of T2 where I shift down two gears and spin out any lactic acid build up. Into transition again, (shoes are on the bike at this point), rack bike, off with helmet (you have to keep your helmet on and clipped any time your bike is unracked). On with the running shoes and out of transition. I'm a fairly decent running and can go really hard the first mile, so I do. Lot of people struggle the first mile (you have a dead legs feeling, which is normal), and I've experimented with going out slower the first mile, but then I really struggle to get going, so I'm actually better off just going out hard, keeping the second mile slightly more moderate and then giving it all my last mile (if a 5k run).

Most important lesson, have fun. Not everything is going to go perfect, but you'll learn for your mistakes, and just keep smiling. When something doesn't go according to plan, just think that it'll happen to every one in a race, so you've lost nothing.