Hi
I have been following your thread and firstly would like to say how brilliant it is that you have really thought about the reality of getting a dog. Any dog you have will be with you a long time and have a big impact on your lifestyle, a lot of people don't think about that.
However, I think you can also 'over think' things too much too, you have managed to bring up two children, a dog is not dissimilar and from what I have read here, you will be fine, so stop stressing!
Don't discount a younger dog, or even a puppy from rescue ( please don't go and buy one specifically from a breeder, there are too many unwanted ones out there that need you!). A puppy is hard work initially, but if you invest time and effort in the first 6 months, you will get a great result, and puppy doesn't mean 8 weeks old, lots come into rescue 16 week - 6 month period, because they are not being clean, still nipping and no longer cute, these dogs are ideal, because with the right input, a dog this age is extremely trainable and you are half way through the worst of it!
Do keep in touch with the Dogs Trust, they literally have dogs in day by day and the younger, good with kids and cats go very quickly. It sounds great to take on an older dog, but your otherhalf is right in that you don't know what you are getting. Most people when handing an older dog into rescue, do not give the full truth. I say 'most' because there are some genuine ones. Your lack of experience and the fact you have younger children around, would make me cautious of placing an older dog with unknown history.
If you are not sure what size or breed, can I suggest you take a visit to www.crufts.org.uk/ and wander around Discover Dogs, see the size of some of the breeds, chat to the owners, most of whom will be involved with breed rescue, find out what these dogs are like to live with and then you will get an idea of the sort of traits that may come through in any cross that you are thinking of.
Can I also suggest that you invest in Perfect Puppy or Puppy School by Gwen Bailey, both books have a lot of common sense and advice for anyone taking on a young dog.
P.S. personally I think taking some time off and settling a dog in is a brilliant idea, makes sure that you do teach the dog it can be left alone in that time and before you return to work you get your dog used to the hours it will be left - but that is common sense and you seem to have that anyway!
Best of luck, it is fun and hard work [she says with 13 wk old puppy flaked out in his bed beside her]. But I don't regret it one minute!