Best thing you can do is take a picnic with you and flasks of tea and coffee and walk from Sluice House Car Park alongside the loch to the Vane Farm Nature Reserve. Stop off at the hides along the way to birdspot and when you come to the nature reserve cafe, pop inside if you want to see the cafe and use the equipment to watch the birds or go downstairs to the souvenir shop. There are toilets for all below with baby changing facilities downstairs which has a ramp for access as well as stairs. Just have to look.
Take your picnic to one of the benches outside and you will avoid the 2 quid cost of a coffee, etc. Nicely presented and if you want to take the woodland walks etc it is 10 quid for a family ticket or 5 quid for an adult.
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