I too am no expert at this, but I was talking with a BASH(Bay Area Siberian Husky) Rescue volunteer about crating recently and she said that crating is OK, but usually not more than 4 hours during the day(at a stretch), or overnight when they are sleeping. It's good that you are able to make it home during lunch hour, because it would probably be unfair to the dog to be crated so much day and night. Like Jackie mentioned, a gated kitchen would be better if you opt to skip the lunch break, so they have a little more room to move around while everyone is gone all day. Do you have a backyard? Could you possibly put a doggie door in?
I think what you are doing currently is better than leaving them crated all day, unless you can get someone to come and let them out for awhile in the middle of the day to go to the bathroom and stretch their legs.

Good luck!