Hard to guess what higher education will look like and cost in 15 years. If costs continue on the trend they are on now, then I would say no, you definitely don't have enough to cover two children's room and board for 4 years.
However, a few things. You don't have to cover 100% of their college. My wife and I will likely be capable of covering 100% but both of us feel it would be better for our children if we only cover half. That way they are motivated to seek out scholarships/grants, and get the grades to put themselves in the best position to get them. And once they are in college, we feel they'll be less likely to blow money on stupid stuff if they see a direct connection between spending and debt.
Also, there are other ways you could cover their tuition if it becomes needed. You could use the principal of Roth IRA's, for example. Or, you may just be able to float it with your income if you are still working. You are on this site, so you are likely saving a large percentage of your income. For a few years, you could just save less and divert some of that money towards their schooling without it effecting your lifestyle one bit. Just a few ideas to think about.