Skye is worth a few days on the way if you have the time. Visitor centre and accomodation office in Portree, plenty of B&Bs there and elsewhere, Occasional pub music sessions, ceilidhs for the tourists and concerts all possible. Stornoway also has good range of B&Bs. I was there in September a couple of years ago and had no trouble finding places to stay - also used some of the independent hostels that abound - particularly recommend Garenin Black House hostel, not far from Callanish Stone Circle and Carloway Broch, also Am Bothan (The Bunkhouse) in Leverborough. In July you would be well advised to book ahead. Also be aware that Sunday observance is still taken very seriously in Lewis and Harris, You can still travel around (provided you filled up on Saturday) but shops, cafes etc may not be available.
If you can, get an Island-Hopper ticket that will allow you to follow the Hebridean chain of islands (some are joined by causeways) down to Barra (look out for the Vatersay Boys anywhere on route), then back to Oban. Fantastic beaches all to yourself.
Have a great trip.
Ross