Perhaps before you invest in an inground pool you could try an above ground pool for a season and see how much use you get out of it.
This type is quite popular here.
http://discountpoolsupply.com/above-...BjkaAkHt8P8HAQ
We had a shallow one when the kids were little and I was working full time. Although there are lots of places to swim nearby, some days it was nice to just sit in the back yard. I did learn years later that pool chemicals should not be stored together or indoors.
As far as the dog goes, does he like swimming and the water? We had a border collie lab cross when we had the above ground pool, it was impossible to keep her out of it, but she loved swimming.
Solar water heating systems can help with the cost of heating the pool early in the season.
Where I live hot tubs are much more common than pools and can be used year round.