Since you're new here, check out the motor oil articles to get a decent understanding of motor oil:
http://www.bobistheoilguy.com/motor-oil-101/
Read the first three or four articles, and you'll see that 0w-20 and 5w-20 are both the same weight at operating temperatures, but that the 0w will be thinner in cold temperatures. Though depending on the temperatures where you live, the difference may be minimal.
As for your cars, what's the oil change interval (OCI) you do on them? It changes what oils we'd recommend depending on how long you go between oil changes. Also, do your vehicles have oil life monitors (a setting on the vehicle that counts down the oil life and tells you when to change the oil).
Without knowing more about the vehicles (how often the oil is changed, driving conditions, etc), it's difficult for us to give you a definitive answer.
Here are some kind of generic answers that might help you until we get more info.
If you choose to go with conventional oils, I suggest Mobil Super 5000 (MS5k). It's a high quality conventional oil, and it ran really smooth and quiet in my car when I used it. As an added bonus, it's the second cheapest oil at Walmart, where you said you would like to purchase your oil from. The cheapest oil at Walmart is Super Tech oil, and both the conventional and synthetic versions of it are really good and excellent values.
You'll have a lot of people on here tell you to go with Pennzoil Yellow Bottle (PYB), it's the current favorite conventional oil on here that people are swooning over. Rightfully so, it's arguably the best conventional oil on the market (MS5k is also up there with the best of them). The reason I don't recommend PYB as a conventional oil is simply that it costs a couple dollars more than the MS5k, and if you're going to pay a couple dollars more for another conventional oil you could pay another $1.50 more than the cost of the 5 quart jug of PYB and get the 5 quart jug of Pennzoil Gold. Pennzoil Gold is Pennzoil's semi-synthetic oil, and according to what's written on the bottle, it's at least 50% synthetic oil. So if you're getting PYB, I feel it's worth paying the small amount more to get the semi-synthetic version of the oil.
If you want to use a synthetic oil, you'll have a lot of people who will suggest Mobil 1 (M1). Mobil makes excellent oils, and they are by far and away the #1 synthetic oil on the market (by volume sold). Protection wise, you can't go wrong with M1, or any of the other synthetics you'll find at Walmart like Pennzoil Platinum (PP), Pennzoil Ultra (PU), Valvoline SynPower, or even SuperTech synthetic. Personally, I've used M1, PP, and Valvoline SynPower, and I think all of them exceeded the needs of my engine. M1 was the loudest in my car, and other people have reported the same thing. However, a lot of people don't hear any difference regardless of what oil they use, so it depends on the driver and vehicle I guess. Please note, that although M1 was louder in my car, I have no reason to doubt it's ability to lubricate and protect the engine; M1 is an excellent oil. On the other end, Valvoline SynPower (and Valvoline MaxLife full synthetic) was the smoothest and quietest oil I ever used.
Any of those synthetics will treat you well. One thing that might help you decide is that there's currently a rebate on M1. Buy 5 quarts of M1 and get $12 back by mail. So you could buy two 5 quart bottles of oil (one for each car) and get $24 back.
Another alternative is to get Motorcraft oil. Motorcraft is a brand that's basically owned by Ford and makes parts to Ford's specifications. So Motorcraft oil is made to Ford's specifications, and has an excellent track record of not only being excellent in Fords, but being an excellent oil for anyone who needs a 5w-20.
As mentioned, not knowing anything else about the vehicles makes it difficult for us to suggest what to do. But because of the rebate, I'd suggest going with M1 0w-20, or going with M1 High Mileage (HM) 5w-20 if you wanted to go with a HM oil. Worse case, you pick it up b/c of the rebates and use it while you do more oil research to identify what you want to use in those cars.
Okay, it's late and I'm tired and rambling. Hope this helped.