DreamingBig - sounds like you guys are doing pretty well. We're about the same age (a tad younger), similar income, two young kids as well.
The main advice I can give you about upping that saving rate, is to really analyze what you are spending your money on. We took every bank statement from the last year, categorized every item, and built a giant spreadsheet out of it. Despite being pretty frugal, a lot of things jumped out at us when we did that, and it gave us lots of obvious areas to attack. It's surprising, even when watching your finances fairly closely, how much the reality differs from your perception of it before really crunching the numbers.
We ranked all our expenses as either essential, important, nice, semi-silly, or downright dumb. Everything that was dumb, we got rid of. Same with most of the semi-silly. For nice, we defined a weekly/monthly allowance, and for the essential and important things, we just trimmed it a bit where possible. It's been taking some will power for sure, but the results were pretty amazing - $2000 per month off our spending!