When you say "Max our 401Ks", do you mean 18K per year each (plus catch up if you're 50 or over)? If you're less than that on the employee deferrals, an individual 401K would let you defer more than a SEP on 15K of income. If you're meeting the IRS limit at work, then you can defer just as much with a SEP as an i401K.
SEP / employer side of i401K is going to be 20% of (net business income less 1/2 self employment tax).
Do either of you work for government? If so, you may have a 457 plan available in addition to a 401K. Other than that, you can cover certain expenses (health, childcare, transit, probably a few others) through FSAs if your employer offers that.
Depending on your income, you might be able to deduct some or all of a traditional IRA.
So, read that benefits packet.