yes, actually ginger ale (be sure and get the kind that says REAL ginger on the label) can help settle the tummy. But both gingerale and 7up are good to drink when you're sick.
As patient915 said above, the carbonation may cause some gas or pain in your belly, but one way you can help reduce or avoid that would be to either let a glass of the ginger ale or 7up sit out for a couple of hours to "go flat" before you drink it, or, you can "filter" the soda through either cheesecloth stretched over the top of a glass or even through a couple of CLEAN cotton men's handkerchiefs.
You may also find that room temperature drinks are easier to tolerate than refridgerated ones at first. So just sitting the soda out to "de-fizz" would help solve both things - the carbonation AND the cold.
While you definitely want to stay hydrated when you're having vomiting and/or diarrhea, it's also important to take these liquids slowly. Just a sip or two every few minutes is much better than trying to gulp down a lot at a time. Your stomach will be much better able to handle a sip or two every 10 minutes than it would be able to handle a full 8 oz glass.
Another good thing to have on hand and drink when you've got vomiting and/or diarrhea is gatorade or other sports-type drinks. These not only help replenish just liquid, but they also help to replenish essential electrolytes such as sodium and potassium. Again, your stomach may handle these better room temperature at first and definitely again, small sips frequently at first.
Also, popsicles or icie pops are good to have on hand when you've got stomach troubles. Sometimes it's easier and more soothing just to let those kind of melt in your mouth rather than trying to actually drink something.
I know you specifically only asked about 7up an dgingerale, but I wanted to give you some other suggestions for when you or a loved one isn't feeling well.
Welcome to the gastroenterology community! Yes it is okay to do this, and many people find that it helps. The carbonation can make you gassy and need to burp.