You are planning a truly wonderful trip to Donegal and we have no doubt you will enjoy your time in our beautiful county.
To further help you with the planning, I'm sending you link to our Donegal Tourism Brochure / Holiday Guide where you will find further information about Things To Do and Places To Go. On pages 24-29 you can find details & specially designed maps of 6 Scenic Touring Routes in Donegal that will help you with your planning:http://wildatlanticdonegal.com/wp-content/uploads/2016/01/%C2%A9-Donegal-Tourism-Holiday-Guide-2016.pdf
Regarding your itinerary, here are further suggestions:
Day 1) You will mainly follow the Wild Atlantic Way (WAW) route, as well as the Inishowen 100 route. There are plenty of the WAW Discovery Points along the way. They are a great photo opportunity; information panels are available at each point. All of them are marked with red star on our map. On arrival, I would suggest that you call into one of the local Post Offices to pick up the Wild Atlantic Way Passport that will allow you to collect stamps from all visited Discovery Points along the way.
I would highly recommend stopping by at Buncrana Tourism Office and speak to Visit Inishowen Team. Here is also their website, if you wish to make contact with them in advance about Inishowen specifically: http://visitinishowen.com/
When in Greencastle, you should definitely visit Inishowen Maritime Museum & Planetarium: http://inishowenmaritime.com/
Day 4) On your shorter day around Burtonport/Dungloe area, we would recommend that you take a Blue or Red Ferry from Burtonport to Arranmore Island, which is approx. 15min crossing. You can take your car with you. This would be a fantastic opportunity to visit one of Donegal's Islands. Alternatively, you could book a Sea Safari & Marine Heritage Tour (boat trip) around the island with lovely Jim Muldowney. Here are further details: https://www.divearranmore.com/sea-safari.php
Perhaps you could leave Portnoo for your relaxing day 7. As you are going to be in the area that day, we would also highly recommend visiting Port Famine village, an abandoned picturesque village in a very remote location north of Glencolmcille, a real hidden gem. You could do it on your way back from Glencolmcille but your day 2 looks pretty busy already or you could leave it for the very last day and really enjoy the experience: https://www.tripadvisor.ie/Attraction_Review-g186602-d7788058-Reviews-The_Deserted_Village_of_Port-Donegal_Town_County_Donegal.html
Also, just outside Ardara - don't miss the Maghera Beach & Caves: https://www.tripadvisor.ie/Attraction_Review-g212511-d4436995-Reviews-Maghera_Beach_and_Caves-Ardara_County_Donegal.html
If you have any further queries, please contact me on: firstname.lastname@example.org
I will be more than happy to help you. If you wish, you could provide me with your postal address and I will send you a hard copy of our brochure & map.
I hope this will be of help.