Hi, Ellen. I think there is a lot of good information in your previous thread. I'm not sure anyone can tell you exactly which 2 of the 3 places to pick. From Emily's post and other information I've gleaned from poking around the web, I don't think snow is going to be a huge problem for you, but issues might pop up. For example, my understanding is that Vršič Pass is generally open by the beginning of May, but it apparently had to be closed on May 9 last year due to a late season snow storm that dumped a foot of snow on the area. I looked at a couple of reviews of the Solčava Panoramic Road from people who did it in May -- one said it was great, one said it was great except they met a road block that kept them from reaching 2 sites.
Bohinj/Bled may be best set up for easy hikes. There's Vintgar Gorge (expected to open in April if no excessive damage from winter snow/ice) -- the out and back walk is easy. Mostnica Gorge is a valley hike that is gorgeous and leads to Mostnica Falls and its nearby restaurant (I took Emily's recommendation to eat the blueberry strudel -- it was great!). The Bohinj cable car should be running and (on a sunny day) would give you a nice view over of the mountains from on high and a nice view of the valley. You could also use the area as a base to visit medieval Radovljica and other nearby towns.
The Soča Valley has some reasonably flat hikes. I did some valley hikes with herbalist and tour guide Vesna from Slocally. It was helpful to have 2 cars so that we could park at one spot and then drive to a second spot and hike back to one of the cars. Her prices are very reasonable, and she offers an assortment of excursions in the Soča Valley and the adjacent Goriška Brda wine region. The cable car for the area (Kanin) will not be running in May, so there will be no easy way to get up high and see the mountains from above.
The Logarska dolina area also has options. There is a nice flat out-and-back hike for Robanov kot valley that starts at the restaurant/guesthouse mentioned in the previous thread. There is what is considered an easy, short hike to the base of Rinka Waterfall, but I saw a review from one older person complaining that the incline to get there was too steep (it is a little steep). The Solčava Panoramic Road was delightful, but I did it with a guide, too -- the very kind Mojca; we ended our day in her mother's kitchen, drinking warm mountain herbal and talking with her family.
So... what tempts you?
I would think your best bet (especially with where you are coming from, including a stop at Škocjan Caves), an itinerary that looked like Soča Valley x 3 nights and then Bled-Bohinj x 4 nights makes the most sense. While I'm not a fan of one-night stays, I would encourage you to even consider taking a night from Bled-Bohinj and spending a night in Ljubljana. As others have mentioned, it really is a lovely place.