Yes me dear girl, Vegas seems to be the venue of choice these days! Since I absolutely love any excuse to get all girlied up, I have some fabulous ideas for great evening wear for you. Rule number one: just like they say in "What Not To Wear", no mini-skirts after 35, so stick with gowns and skirts that hit right at the knee, or just below. You can get away with tea length dresses and skirts if you have slender calves, otherwise go with knee length or floor length.
If you have great arms, go with a sexy halter-style dress. The halter-style is very flattering, as long as it is not too plunging (then you just look like you are trying too hard). It also has the added benefit of providing a little more coverage around the side of the bustline and on under the armpit, and can hide some of those gravity-induced sags and bulges that begin to appear as you age. If you are well-endowed, be sure there is adequate fabric in the bodice to ensure that you aren't bursting out all over. A strategically placed brooch or pin can help keep the neckline together if it tends to be too plunging or too bare.
Unless your arms are in very good shape, I would stay away from strapless or spaghetti strap dresses. They tend to dig in to the shoulder area, causing unsightly bulging along the arms, back and neckline. You can still go sleeveless, just opt for a dress with wider, softer straps - perhaps a tank style dress or even a cap sleeve dress. A floaty skirt and sexy top is also another option. As are palazzo pants and a chic blouse. Finish your ensemble with some fun jewelry.
Footwear is one area you can really play up in Vegas. Metallics, shoes with embellishment and bada bling, patent leather and animal prints - anything goes baby! Just make sure you can walk comfortably! Also, choose a handbag with a little attitude, but preferably one with a shoulder strap or chain strap so you can keep it close.