A live butterfly garden contains two elements, if the area is large enough. The first is food sources for adults, which might be flowers, fruit, carcasses, tree sap, etc. The second is larval host plants. Please check literature of your area about the butterflies found there, then see if you have space to introduce the larval host plants in an undisturbed part of the garden. Usually, introducing one or two individual larval host plants will not succeed in attracting females to lay eggs, there have to be numbers of the host plants. Observe which flowers attract which butterflies in which season and then plant them accordingly in the part of the garden accessible to visitors. Good luck!
Since decades I like to photograph (and sometimes grow and let free) some butterflies (and moths). Therefore, I also had some interest in visiting butterfly gardens in Germany and everywhere I worked or lived. During the last 30 years they seem to increase a lot. I really liked several ones in Germany, California and Florida. Maybe you contact those gardens. Depending on the climate, you may be able to have a combination of both, a garden area with free access of wild butterflies to a selection of plants (flowers, but also those for the larvae), and a garden house which allows exotic butterflies to fly and be seen by the visitors. That often includes many butterflies from butterfly farms (I think in south america) growing the larvae and sending them internationally - and the visitors can see some of the butterflies, for example, some swallowtails on citric/orange trees to eat the leaves. But one major question is how to protect the butterflies and the plants. Some gardens may make the initial mistake to put in some new plants for the larvae, but overlook that those normal plants often come from sources which used insecticides... (so the butterfly larvae can not develop). Good luck!
PS: Since I've seen many butterfly "houses", often surrounded by a (butterfly) "garden", I just looked up the link for the one in Florida which impressed me a lot, so I visited regularly - but I have not commercial connection to it. Basically, all international butterfly houses appear to have the same (easy to keep?) species, but this one is in my view, very unique, since it even offers the visitors to buy some of the plants they can grow in their garden to attract butterflies.
I should also mention, growing the larvae yourself and not buying them as a regular supply may increase the risk of also growing some butterfly viruses. Usually those butterfly houses are used for educational purposes, so families and school classes can (over)crowd the garden, but there are also times with less public traffic.
That specific garden also included wide areas for walking and different houses with specific educational background, but also relaxing areas - but also included hummingbird houses one could walk into, but that is not related to butterflies.