Abbotsbury Swannery is well worth a visit, and is excellent for the disabled, with wheelchairs that you can borrow to go around the site on good paths and pretty level all the way around. If you are disabled you can park at the bottom right by the entrance.
The swans and cygnets are in individual pen areas with an open area on the lagoon looking out at Chesil beach which has lots of swans, Canada geese and other birds. There is a picnic area on the site which we used so we could see the birds all around us as we ate. We watched the feeding time at midday which was good fun, and many children joined in with feeding the birds.
It is a lovely spot and you feel you are in a secret lagoon location surrounded by the birds and reeds as you walk around the site. You can take a passport ticket to visit the Abbotsbury Subtropical gardens and Children's Farm if you wish to make a day of it. There is a cafe at the entrance.