There are a lot of different ways to do things, but I'm going to lean towards more 401k contribution vs. going taxable. For the long haul costs matter - a lot - so the advantages of tax-free growth even if you didn't get a tax deduction for the contribution are very worthwhile.
If you are in the 10% or 15% tax bracket, then you do not have to pay long term capital gains tax. In 2013, the top of the 15% tax bracket for married joint filers is $72,500. With zero federal tax liability and, at least in the medium term, little benefit to the tax efficiency of a 401k, I would recommend that they have they invest the money in a taxable account. The cost of locking their money up in a 401k, is not worth the benefits in the current situation in my opinion.
Cottonwood, congratulations on your families financial position. You are both doing an excellent job of being financially responsible. If you do decide to go the 401k/IRA route, if it is possible (not sure about rules on this), I would suggest looking into opening up an individual traditional IRA account as it would likely give you a lot more flexibility in what you can choose to invest in relative to a 401k plan through your husbands employer (still take advantage of entire 401k employer match).