Hi Richard
I know this area well as I worked there for a couple of year before College and often return to visit friends. What time of year are you talking about? as there are obviously more sites open in Summer time.
There are absolutely loads of good site in the Dalbeattie area. Some sites I would recommend are:
Castlepoint Caravan Park, Rockliffe By Dalbeattie. Tel 01556 630248 This site has sea views and is located in the picturesque seaside village of Rockcliffe about 4 miles from Dalbeattie. We had a very pleasant week there a couple of years back.
Kippford Holiday Park, Kippford by Dalbeattie. Tel 01556620636. This is near to the above site. I've not stayed but I've heard good reports.
Sandyhills Bay Leisure, Sandyhills, by Dalbeattie. Tel: 01557870267. A coastal site not far from Dalbeattie and next to a good beach.
The Park of the Brandleheys, Crocketford. Tel:0845 4561760. This park is inland near to the A75 road from Dumfries. I've not stayed, we like coastal sites, but it has won loads of awards and has a good reputation.
Lochside Camping and Caravan Park, Castle Douglas. Tel:01556 502949 (only 9-5 hours) An unusual park in that it is owned and run by the Castle Douglas Town Council. It is an area of the town park with a choice of tarred pitche or grass. It has lovely views over the small Loch. We have stayed here often both visiting local friends and when driving through enroute to places further west.
Mossyard Caravan Park, Gatehouse of Fleet. Tel: 01557 840251. A lovely coastal site with its own beach on a working farm. I know the site well but since being a caravanner I have never managed to get a pitch as they get very booked up school holiday times and we're both teachers!!! - you may be more fortunate out of school hols. This is further west than the others but very close to A75 so not too far to drive to the Dalbeattie area.
Brighouse Bay, Borgue, Kirkcudbright. Tel:01557 870267. A large coastal site with a lot of activities but not in an overcommercialised way. We've stayed here a few years back when our kids were still kids.
I hope this helps. I could easily list another dozen good sites. Post again if you've got any further questions. I'd recommend www.ukcampsite.co.uk website which has a campsite search facility with reviews. I've put on reviews of some of the above site on there.
I see, by the way that you're not too far away from us - we live in St Helens.
Best wishes
Tim