Small cruise ship vs ferries around islands of Dalmatian coast

Hvar and Korcula would be somewhat manageable but I think you would need a car at the very least. If this is a no go then a small ship may make the most sense. Just be aware that there are many different styles of travelers that these boats appeal to from people such as yourselves to younger folks looking to party and hook up.

No need for a car at all when you travel by boat. www.FerryHopper.com lists the schedules and fares for Croatian ferries and the high-speed catamarans such as the Krilo Catamaran and the new TP Line.
There are dozens of islands on the Dalmatian Coast the boats stop at. A popularly-traveled route starts at Split and then visits Hvar, ( 1-hour by catamaran) Korcula ( 90-minutes from Hvar by catamaran) and finally Dubrovnik ( two hours from Korcula by catamaran). There are lots of variations to this itinerary including reversing the order of islands. You can pre-book catamaran/ferry tickets online, or buy them in each port a day or two before you plan to travel.
As far as carrying your luggage— if you simply take the typical roller carry-on aboard flights along with a shoulder bag, you just roll that same carry-on aboard the boats. You are responsible for moving your own luggage. On a catamaran, roller carry-ons are stored inside the front of the boat’s cabin where all the passengers are seated. Shoulder bags you keep with you.

I don't think need a car for this plan--it would limit you to car ferries for one thing, when catamarans (passenger only) are much more common and frequent. It helps if you show us what sources you are looking at (describing it as complicated). I use the Krilo and Jadrolinija websites for schedules. There are a couple other operators as well, but those are the primary ones. What islands are you interested in, how much time do you have, and where are you flying in/out?
Pack one suitcase that you can roll--problem solved!

We rented a car but I spent some time researching taking the ferries on your own. It looked like there were baggage storage locations near the ferry stops. You'd have to carry or roll your bags there. Or, if spending the night, book accommodations with luggage storage. It looks like a fun way to travel!

Cruises are different animals obviously, but traveling by the passenger ferries couldn’t be easier. I would DIY it as long as you’re staying a couple nights in places like Korcula or Hvar. If you’re thinking more like “island-hopping” like you’re there for an afternoon, then I’d look at a cruise.

Worth noting all the major port towns have their own local fleet of excursion boats to take tourists around the area.

Thanks for all the advice. Looks like we'll try the ferries

My husband and I just got back from a 7-night small ship cruise (38 passengers max), Trogir to Dubrovnik and really enjoyed it. We usually got into port right after lunch and you could do what the cruise had planned for you or go off on your own. Dinner was on your own so it gave us the chance to try different restaurants. It was through Katarina Cruises. Feel free to message me if you'd like more feedback.