June is a great time to go. Very crowded in July and August. There is lots of good information on these forums about bareboating in general - check it out. A thorough checkout list is a must. Make sure you go thru everything and ask questions. Provisioning can be an adventure for new bareboaters. The restaurants in Croatia are fabulous and part of the adventure is walking the town quay to town and checking out the restaurants. We provisioned mostly for breakfast and lunch.
If you and your wife are experienced you should be fine. The Med-moor can be intimidating if you haven't done it before, but our crew (3 experienced, 4 not so much) did fine. If you haven't bareboated before, I would stick with a well known company, ie. Moorings, Sunsail, Navigare to be sure there is a high level of support if you need it.
-Dave