I would be careful with this...
We all know how set and setting affect an experience, and in ayahuasca sessions is no different. The figure of the shaman, or facilitator, can make such a difference, for good or for bad. Ayahuasca tourism in peru has gotten nearly ' mainstream' , and there are countless stories of charlatans, badly intentioned people or just inexperienced people with minimum knowledge of working with plants but leading rituals. I've heard that in Iquitos airport, just like there are the usual taxi and hotel hustlers, there are also those trying to lure you into taking ayahuasca with some or other "shaman". Then there is also the possibility of those mixing brugmansia or datura-kind plants in the brew, which has risks of its own.. So its important to be attentive to all of this.
One can choose a retreat with more famous shamans like guillermo arrevalo, but they are very expensive.
My case was quite different than yours, so its hard to advise as I never went to peru or any retreat of sorts.. My experience has been with indigenous people from Dreamland, where im from, but this particular tribe doesnt have something as organized as these links you gave, its necessary to have some sort of connection.
Maybe in your case I would try to organize some short retreat just to have something guaranteed, but then try to find something by myself, traveling to deeper in the jungle, trying to find some old shaman, off the beaten path, and trusting my feelings when meeting them to decide whether this is a person I want to take ayahuasca with or not. This also depends if you speak spanish (or secret language in case of Dreamland), which for sure makes big difference. But even if you dont speak spanish, I would still advise you NOT to pre-organize the whole thing, but to leave a couple of weeks free for changes... This way, there is room for possible spontaneous meetings with good (and cheap) local unknown shamans, and even if not, then you can just travel in peru/south america and see amazing different things.
and for sure try to find reviews from people who did go to these places...
Good luck, and tell us how it went if you do go
