Investing isn't always the most exciting topic of discussion for kids. That's old-person "stuff." But we all know the value of time as it relates to saving, which is particularly true when considering stocks. A discussion of stocks also gives us the chance to share the concepts of long-term growth, income, and risk.

But are some stocks more kid-friendly than others? We asked a few Fool contributors that question, and for a variety of reasons, ExxonMobil Corporation (NYSE:XOM), Under Armour (NYSE:UAA) and Facebook (NASDAQ:FB) all stood out as suitable stocks for a youngster's portfolio.

Bob Ciura: When I think of stocks to buy for kids, the first thing that comes to mind is a business model that is viable over the long term. If I were to buy a stock for children, I would want to be sure that I'm buying a stable business that has stood the test of time. Although the energy sector looks dangerous at the present time, I still believe in ExxonMobil over the next 10 years or longer.

To be sure, the energy sector is really suffering right now. Even the biggest and strongest oil majors like ExxonMobil are struggling from the more than 50% drop in oil prices over the past year. That is why ExxonMobil's profits fell 52% last quarter, year over year, to $4.1 billion. Earnings per share fell 51% to $1.00 for the quarter.

But despite this, if investors believe in the long-term future of the oil and gas industry, then today's turmoil serves as a great buying opportunity. Shares of ExxonMobil have fallen back to 2011 levels. Its dividend yield exceeds 3.7%, which represents a 10-year high. But ExxonMobil has the highest credit rating in its peer group, and earlier this year actually increased its dividend, which demonstrates its resilience in a brutal operating climate.

That's why, even though it's hard to see any light at the end of the tunnel, I believe long-term investors will look back at this price and realize ExxonMobil was a huge bargain.

Tim BruggerThere were a couple of reasons the first stock I bought for my kids was Disney. Not only did it offer a relatively consistent track record and strong growth prospects, but it made for an easy transition to discuss investing. Who doesn't know Disneyland, Cinderella, and Mickey Mouse -- and now they had a chance to own a piece of all that? For many of the same reasons, Facebook is a great stock for kids.

As of its recently completed Q2, Facebook now boasts 1.49 billion monthly average users, of which 1.31 billion are of the mobile variety. Even more impressively, just shy of 1 billion users access Facebook every day. Now, include WhatsApp's 800 million MAUs, Messenger's 700 million-plus, and Instagram's over 300 million users -- many of whom are teens, and it's safe to say your kids are counted among the Facebook family of apps. The likelihood that your kids are on Facebook makes the discussion of investing a natural: It's one thing to use the site, another to own a piece of it.

Of course, familiarity in and of itself is hardly a reason to invest. However, Facebook also offers a host of long-term growth opportunities. The advent of video earlier this year as an advertising alternative across Facebook is already paying dividends. COO Sheryl Sandberg wouldn't give specifics, but video has certainly made a positive impact on revenues and "continues to be a priority." With word that Facebook is (finally) ready to fully monetize Instagram -- including video spots -- another key growth driver is ready to push sales even higher.

Not only will kids love the notion of owning a piece of Facebook, opening the investment discussion doors, but it offers tremendous long-term upside.

Joe Tenebruso: When I think of the perfect stock for kids, the first thing I look for is a simple, easy-to-understand business model. That's because the biggest benefit we can give our children may not be a stash of cash, but rather an education on how to recognize and invest in great businesses.

Sports apparel maker Under Armour fits this description well. The business is relatively easy to comprehend, and, importantly, it's one that many kids can relate to. Under Armour's clothing is popular among kids and especially young athletes, who often aspire to wear what their sports heroes are wearing -- and the pros are increasingly outfitted by Under Armour.

Secondly, I look for a long growth runway. That's because when we invest on behalf of our children (or even better, if they invest for themselves), we're typically dealing with an ultra-long-term investment horizon. Even if these funds are earmarked for education purposes, they often won't be needed for a decade or more. Companies like Under Armour that have years and potentially even decades of growth ahead allow us to profit from this investment time frame.

 At 68 times forward earnings estimates, Under Armour may seem expensive today, but with profits that are expected to grow at nearly 25% per year for the next half-decade, it's quite possible that shares will prove to be a bargain in the years ahead. So rather than worrying about what appears to be a premium-priced stock and a potential short-term pullback in price, we can calmly and patiently invest in an outstanding growth company and profit as it fulfills its long-term potential.