Your husband might change his mind when he actually meets the dog and he can see how your kids love it. Most people come round eventually. Us not having a dog has always been a huge complaint of dh's, he would really love a dog but I've refused because he was only home an hour or so in the evenings and I would have ended up with all the work and I've never been keen on the idea.
I need to work on my own list, clearly...
That's good that eldest has been thinking about it, maybe you can take something of a back seat in this situation and let him and H drive most of it.