Hi Krishna

We went to Rovinj 3 years ago , and I posted a review here
http://www.holidaytruths.co.uk/reviews/croatia/rovinj/

The area round Rovinj is great for walking, and the town is very picturesque. There are also boat trips to go on, and as I mention in my report, a day trip to Venice.
I fear that he will be a bit cut off at the Hotel Istra, as the island it is on, is very small. Unless he likes that sort of quirkiness on holiday. There is a frequent ferry service to the mainland, but it would irritate me to have to rely on that to get around.
We stayed at the Park Hotel, which is owned by the same group. It was very good when we were there, and there was a huge choice of food.

I haven't been to the other two resorts you mentioned, so I can't comment on them.

Hope this helps