We need to see th whole space and aslo how you get from the house to the space .There is no context for us to begin to help Post the pics here in a comment DO NOT start another post and not screen shots from your phone that we can't enlarge

You need a local source at your home, pavers and probably some fill soil first, to create a safer leveling. You aren't going to do it yourself, so a local landscape specialist near you will be far more helpful.

I agree this is not a DIY for you but a plan could help .

A ramp from the house to the level of the patio. Stamped or plain concrete or stones set in mortar. I wouldn't do pavers or anything set in sand--they will eventually move and the patio will no longer be level and safe. And yes, get a good hardscaping contractor.

I'd need some more information:

Is the ground cover good to walk on, or do you want to stick to pavement or pavers?

What are the current safety issues?

Is sitting at the table a safety problem?

We need to see how you get from the house to the garden and have a description of where your difficulties are.

What are the dimensions of the space?

You may want to get quote from contractors, but thinking about how to describe your needs will be helpful.

Pavers are not walker or wheelchair friendly. Concrete with a fairly smooth surface will be best.

I'm envisioning concrete with two tree pits, nearly where the current trees are still located so it has something living and isn't just a hard surface.

No! to a sea of concrete.

Concrete might be boring but it will be least expensive and safest. No idea what the layout should be with so little information. OP can you use bing or google earth to show us an overhead view of the yard?

I do not love any surface that cuts off water supply to a tree but you need something that wheelchair can move on and thta will need some info from you . So Kendrahs idea might work for the sake of the trees but barely since the roots are way past the trunk. More imporatn is the wheelchair motorized or not.

BTW when we take the time to try to help we need you to answer questions and supply info all done in comments here DO NOT start another post

@Olychick …. Perhaps you aren’t familiar with ADA compliant pavers. That’s what I have, they’re nothing like the old style “cobblestone “ types of years past.

@K Laurence, good to know! I hope if the op decides on pavers s/he will be sure to get that kind. Regular pavers can be hard enough sometimes without mobility issues and especially if they aren't laid on a properly prepared bed.

@Sigrid stamped concrete can look very attractive:

even made to look like wood: