How much should we be saving for retirement?

My husband only works, I am a stay at home mother of four children ( I worked for 8 years as a lab manager before having children). How much should we be saving for retirement? He is 35 years old, I am 36 years old. We currently max out his 401K at 15% of his pre-tax salary. We also save 10% post tax into an annuity type account (life insurance also). When I use retirement calculators, they usually say we should be saving only 5% of our pre-tax income actually since we started at age 26 or so, but I believe that this is only for 1 person, and we are actually saving for both of us. The Yahoo retirement calculator says we should have ,000,000 in all based on 8% return. Should this be ,000,000 instead for 2? We have no debt except for a ,000 mortgage with 9 years left. None of our friends or family save as much as we do, but are we really going overboard here with savings? Or is it better to save as much as we can now and ease up later when our children are in college?
I guess I actually have two questions: With the retirerement calculators, they ask if you are married and if your spouse has any income, but are the totals for one person or two? Also, is a total savings rate of 25% totally off the mark (too much)? My husband thinks we are saving too much, I am very conservative!
Thanks so far for all the answers. With all of our savings as is, and 4 young children with 1 income only, we really have no "disposable"spending money. Is cutting back to 10% for his 401K a good idea? Would our retirement still be "on course" for both of us? We never eat out, have not gone on vacation since we were married 10 years ago, his car is 9 years old and we would need to buy a new one soon, etc. He thinks we need to enjoy our lives now a bit more. We do also fund an HSA with about 4% pretax also each month! But we have no separate college savings plan yet.
I thought that 529 plans only had state tax benefits, not federal currently?