Get your self a copy of the Victoria Cabin, Caravan, and Camping Guide which is available from Parks Victoria for free; or go to their website and look at the parks in the area (see the link below).
Re the specific parks, there are eight with a pool in the High Country, and seven of those have a playground as well.
Check:
Painters Island Caravan Park - Wangaratta
Wangaratta CaravanPark - Wangarata
Bright Pine Valley Tourist Park - Bright
Bright & Districts Caravan Park - Bright
Porepunkah Bridge Caravan Park - Porepunkah
Porepunkah Mill Holiday Park - Porepunkah
Porepunkah Pines Tourist Resort - Porepunkah
There are another eleven parks if you want to go to Lake Eildon and surrounds.
Check out :
http://www.vicparks.com/index.asp