Hi Dot,
We have stayed at The Gart three years running and booked to go again in May. I can highly recommend it, especially if you have children, as part of the playarea is under cover and overall it's a very good playarea, easily seen from many of the pitches.
There are pitches around the perimeter of the park, which are quieter, away from amenities block, playarea and central grass area. As Maureen says the toilet / shower block is up to Caravan Club standards.
It's very easy to get to, good access and arrivals area, friendly staff, no downsides really, maybe not the most spectacular scenery in the area. Some may consider to be a little expensive per night, but I don't. I think all pitches have water / drain.
Callander has supermarkets, bars, restaurants etc.
We also stayed at Maragowan in Killin at the start of the month. This is a peaceful site by the river. Good scenery, short walk into Killin, very small playarea and a wee burn for the kids to splash about in. Caravan Club standard facilities.
We would stay at either again with no hesitation, but we prefer The Gart, mainly due to the fact that it's a shorter drive from Dundee, it feels a bit more spacious and the playarea is a huge factor for us, with an 8 and 4 year old.
Enjoy,
Alex.