Given your requirements, the only options that are not wildly expensive are the Mahindra XEV 9S and the Kia Carens Clavis EV. Both are three-row SUVs that are pretty spacious and practical, but they differ in what they offer.
The Mahindra car comes across as the more premium of the two. It’s larger, has an imposing road presence and comes packed with technology and features. It wins the spec-sheet war and is a very comfortable, compelling option. However, once you consider how the car will be used, the Kia Carens EV could be the better everyday car.

One of the most significant factors is access to the cabin. The Carens Clavis EV sits lower, making getting in and out easier. Your requirement for a wheelchair suggests that someone with limited mobility will be using the car, and this is why the step-in height becomes something you notice every single day and a very important factor.

Also, the third row, too, is slightly more practical and usable in the Kia car. When the third row is folded down, the boot is spacious enough to accommodate a wheelchair. The lower floor also makes loading a wheelchair easier.

On the ownership side, Mahindra’s EVs have made rapid progress and the products are far more polished than before, but some owners still report software-related hiccups. Kia’s EVs, by comparison, are better sorted, suggesting a more predictable ownership experience.
Both cars are easy to drive; the XEV 9S offers a better ride and is more refined, but the Carens Clavis EV feels less cumbersome in tight spaces.
 

The Mahindra XEV 9S is a large car, but its last row isn't comfortable for adults over long drives. Hence, if you need a comfortable seven-seater for long drives, consider the Turbo petrol versions of the Kia Carens Clavis and Tata Safari instead. 

There's also the Kia Carens Clavis EV in this range, which shares its battery+motor with the Creta Electric. However, on your 350km+ highway drives, you will have to stop and charge once, as its real-world highway range is about 345km as per our tests
 

The Kia Carens Clavis EV would be a great choice for you. It is hugely practical with a spacious cabin, the EV powertrain is smooth and efficient, and it isn't uncomfortably large to drive as a daily car. 

It gets a feature-rich cabin, well-sorted ergonomics, comfy ride and seats and Kia's reliability and after-sales. It is a hassle-free car to own, and one that is our top recommendation. 

Buying a diesel does have some level of uncertainty given the constant negativity around it, be it from official statements as to its certified life or restrictions on its usage on heavy air pollution days. 

Thus, if you are open to an electric, we would advise you to go ahead with this. Furthermore, your daily running is low, and even your occasional long distances are 300kms which should be manageable with something like the Kia Carens Clavis EV. 

The Clavis EV also has a nice and premium interior and is very well equipped in typical Kia fashion. The recently launched Mahindra XEV 9S is also a very good option, again with a premium interior and a good equipment list.      

We'd strongly advise you to get a 7-seat EV for times when more family members join in. Of the current options, the Kia Carens Clavis EV is a great option. It is very smooth, offers good performance, and the flexible seating means you can maximise middle row space (when there's only 4 on board) or make more space for the last row (when there are 6 or 7 passengers on board). 

Upcoming 7-seat options include the Mahindra XEV 9S, which will be launched on November 25. Our review of the model goes live later this month. Stay tuned to know if it fits your needs! 

The Hyundai Creta Electric with the long-range battery is a very good option that has features, good range and comfort. If you want more space, the Kia Carens Clavis EV has the same powertrain as the Creta and features set too. Either one of these two will be good.