We always pack our own snorkel equipment on vacation. We always go to a local dive shop to purchase it. They will likely sell a range of different price point products, including some US Diver equipment. I don't think there's anything "wrong" with US Diver equipment if it fits properly (esp. for once a year useage). One thing about buying each piece separately at a dive shop (rather than in an all in one kit) is that you can try the masks on to be sure you get a proper fit (seal). Different masks fit different profile faces (ie thin, skinny vs chubby & round). You can also buy a mask that is rated for different depths, in case you think you would ever want to scuba dive. You probably could not take a $25 mask from Walmart down past probably 20-30 feet. Diving masks will be rated for a deeper depth just like a watch or a camera and will probably be on the higher end of the price spectrum.
I use an RX mask so I am limited to the ones that my shop carries that they can fit with an RX lens. It doesn't have to be as precise as my regular eyeglass RX so I don't go getting new lenses each time I get a new RX. I am on my 2nd RX mask (the first one got a chip on a lens corner and started leaking). The "dry snorkels" are quite a nice idea, especially for kids. Sometimes you can find adustable fins for kids too so that you can let the straps out for them as they grow. (DS now uses fins with his swim club so another spot to look for those is at a team swimwear apparel store.) Oh, and yes, get a small bottle of the anti-fog spray. Spit works too in the interim if you need, but this stuff is good for your initial jump in. Not quite as gross as the spitting.
