This is a great arboretum. There are a lot of spaces to explore, and it seems to cater to everyone. The trails nearby the visitor center are full of things to look at without a lot of walking. There are also several places that seemed accessible to those with limited mobility (though I cannot speak from experience here). You could take a tram tour, or hop in your own car and explore the 3 mile drive yourself. There are also extensive hiking trails.
We could not see it all in the 3 hours we were there. We were visiting friends in Minneapolis, and our friends planned to redeem their admission ticket for $$ off an annual membership, because they could see visiting this place throughout the year.