In Hvar, the wedding ceremony and reception will be at Beach Club Hvar (1 on the map), which is around a 10 minute walk from the main square and wharf (2 and 3 on the above map).
There's no Uber on the island so you'll likely be walking everywhere. When looking for accommodation, you will want to book somewhere in the white area, but try and be close to the centre as it can be a 20+ minute walk into town if you're in the outskirts.