Hi Angie.  
My first trip was to Cilento Coast, incidentally I was on the first trip out there for Just You.  I wasn't sure how I would get on as I had done quite a bit of independent travelling but I really enjoyed it.  The great joy for me was not being alone at night and having someone to chat with over dinner, and over a drink.  
Incidentally I am off to Istrian Coast again this year.  Which date have you booked?  I am going on the September 16th departure.  It's a lovely part of the world, stunning scenery, friendly people and still very reasonable prices for food, drinks etc.  I haven't been to this new hotel that JY are using but I am vaguely familiar with the area.  So if you need to know anything please let me know.  If you are not on my departure have a great time anyway.  You've picked a good holiday for your first trip.  :thumbup:
I agree it's the evenings and meal times it's really good to have company. I have booked to go on 9th September so just before you.
I was wondering having been before which excursions you would recommend. I suffer with Asthma although it's well controlled but would there be any trips you think not suitable. I want a relaxing holiday mainly but I do like to mix it with one or two excursions
The Istrian Explorer (I think that is the right title) is the included trip, and is a nice introduction to the area, visiting Pula, Rovinji and Porec.  Not a huge amount of walking, and I believe that lunch is included in Pula this time.  There is also a stop on the way back for cakes and wine which is fun.  
I know that there is a half day trip to Opatija on Day 2 but personally I think it is expensive.  I believe that there is a local bus that stops right outside the hotel.  It's a nice town with some lovely gardens and interesting buildings and well worth a look round.  
The boat trip is very relaxing and fun.  I don't know if they will be stopping off in Cres as we did when we went from Rabac, but the bbq and wine on board is interesting :)
I haven't done the trip into Slovenia to the caves and the stud farm for years although I was in Slovenia last year.  That is a good trip but take a warm waterproof or jacket as it can get chilly in the caves.  I haven't been to the stud farm since I first went to what was then Yugoslavia back in the 80's.  I may well do this trip.
Plitvice Lakes are WONDERFUL but quite strenuous walking and a lot of steps and walkways over the water without handrails.  Personally I know that I couldn't do the trip now although I long too and don't let me put you off.  :thumbup:  It's a long day and the last part of the journey is on quite windy roads some hairpin bends).
I haven't been on the Motovun trip as that is a new one but I understand it is quite a steep walk up to the village.  
I have slight mobility issues and use a stick so I can only speak for myself.  It sounds as though you have the asthma well under control, but if you want some advice on the trips I would ask your Tour Manager.  If you get Vladka (V), she is wonderful and would be more than happy to advise you.  In any case have a wonderful time.
If you think of anything else please feel free to ask away.  :thumbup: