My dad always says - 'Think of the work uniform for the specific job, then go 20% smarter'. From what you've described, I'd be inclined to go with very smart casual - nice pants and a dressy top for you (like something you'd wear to dinner at a nice restaurant, nothing *too* fancy but something a bit smarter than your everyday wear), and for DH, trousers and a button-down shirt, I don't think a tie or anything is necessary.
Personally I'd rather go overdressed to an interview than underdressed, it just makes a better impact on the interviewer if it looks like you've made an effort to go above and beyond the expectations of the job Best of luck with it, I hope you land the job and that it all works out for you guys! Sounds like a great opportunity!