Little trip...

Early in the morning, we took a bus and headed for Lake Chiemsee. We arrived after a 3 hours drive.
After leaving the bus, we had a huge breakfast with bread, sausages, fish, cheese and, of course, beer.
After that, we took a boat to the island of Herreninsel and Fraueninsel where we walked to visit an amazing castle. We had lunch at a restaurant and enjoyed an amazing view of the lake. There were a lot of birds and ducks which could be fed. We walked back home and everyone could spent 2 hours on their own.
Back at the bus, we ate some snacks and headed back home. This was a memorable, beautiful day.

****you can also use "many" for "a lot" if you wish.

****If the island had two names then you are correct. If it is two islands with two separate names then you would write "we took a boat to the islands of.......)

****I don't think you walked home after seeing the castle, i think you might mean perhaps, "back at the bus station" or "we walked back to our meeting place".

I hope these corrections are helpful.