You might be interested in Flor carpet squares. If one gets soiled/damaged, you can replace just that square. Another option is hospital grade carpeting.

In terms of furniture, you might try looking at furniture used in inpatient psychiatric hospitals. It is heavy, so it cannot be picked up and thrown. It is also pretty much indestructible.

If you get lamps, get them in unbreakable material (ex: metal, wood) and get the kind of light bulbs that do not shatter into small pieces of glass. I saw an advertisement recently for some.

A mid-range blue is usually calming. Accent with small amounts of dark blue (a tweed is often a nice looking way to introduce different colors in a way that is not stark). Secondary colors might include forest green, pale yellow, or a rich color of brown. I would not use any shade of gray or beige. If parents and children are coming to therapy, one does not want them to see colors that are associated with depression.

Art on the walls can be abstract geometric shapes or calm landscapes. Something to gaze at without evoking strong emotions. Use non-breakable "glass" in the picture frames.

A fresh flower bouquet in a basket (never in a glass container) or even a single stem in an unbreakable bud vase at the reception desk makes a bigger impact than you might imagine. Be sure that the species of flower you select is not poisonous if ingested.

Also, consider using Universal Design principles.
The following "mega post" will give you some places to look for more ideas and information.

Houzz
1.) Go to Houzz Ideabooks and enter "Universal Design" in the search box.
2.) Go to Houzz.com/Handicap-accessible
3.) Go to Houzz Design Dilemma and enter "handicapped" in the search box.

Universal Design
1.) www.universaldesignstyle.com
2.) www.schaefferconstruction.com specializes in Universal Design

Handicap Access
1.) The Americans with Disabilities Act (ADA) site has specific measurements for wheelchair turning radius, angle of ramps, handrails, everything.
www.ada.gov/adast94.pdf
www.ada.gov/
2.) ADA Ramps: ADA Code 4.8

Other Houzzers will have different ideas from mine. Please take from this whatever is helpful. Best wishes.

Thank you so much for your thoughtful response to my query. So appreciate it.