Hey there... I have had various problems with PF in the past, and the sandals that I swear by are Chacos. I get the Z2 style, with the toe loop. For me what works best is a firm footbed --- squishy just doesn't give me enough support. These are firm, stable and GREAT on wet ground. Also, they dry amazingly fast.
Regular crocs aren't enough arch for me (part of the problem with my feet was the arch had "fallen" and I have to have a very firm footbed with a pretty stiff arch to have it all work) - I've never tried the Rx ones tho.
I have tried Merrells and they just don't work for me - I want them to! They are too soft a footbed with no where NEAR enough of an arch. Some of them feel downright flat.
I have a couple pair of Keen shoes that are pretty good - their sandals do not work for me tho.
Danskos are also excellent. I mostly wear the traditional clog style, but have found that some of the sandals work - but I don't know about a Disney day in a leather sandal. It just doesn't sound like a good idea!
Birkenstocks are another favorite. I have various pairs and they are all very supportive and they are getting better about being CUTE too! The downside is the cork cannot get wet.
A big thing for me was stretching... as long as I keep my calf/ankle muscles well stretched out, and wear good shoes, I don't have problems with my heels like I did.
The sad part is that now all shoes cost at least $70. On sale. The bonus is they last forever.