Any vets or doctors on here as I need advice

I am neither a Vet Nor a Doctor , but I would put on coveralls and a mask and clean up as much poo as you can , then cut the grass with a mower with a grass box and cut the grass as short as possible , then spray the place with Jeyes Fluid , and keep the kids inside for a fortnight , cutting the grass very short so the sun can kill the bugs . I hope someone else will give you pointers
There are nasties in dog poo

Here is an article that might be helpful.
www.gardenerscorner.co.uk/threads/how-to-disinfect-my-garden.6461/

Chlorine will kill most germs without harming grass very much. You can get it from a swimming pool supplier.

Obviously scope up all you can first.

Warning! Jeyes fluid will kill your grass...!

aggie is correct. There are parasites and other nasties in dog poo, and it needs lifting and getting rid off. Then you need to give the lawn a thorough hard hosing down, let it dry, hose it down, let it dry and so on.

Hopefully the hosing down will dilute any nasties and the exposure to light and sun will kill them. If you can find some disinfectant that will not kill your grass then even better.

I suppose if they are that worried then the simpliest thing would be to returf the lawn?

Found this online

Hose down the yard to spread the feces particles left in the yard. This will make it easier to kill the parasites or virus

Use a 1 to 30 solution of bleach and water. Spray entire lawn using a spray bottle or a pesticide sprayer. Spray all driveways, porches and walkways too to be on safe side

Clean and disinfect the scoop or shovel with disinfectant too

The poor dog - can’t ever have been given a proper walk. Animals hate fouling their own territory.
I’d sigh deeply and, after removing all poo, dig it over and returf. Hope it’s not too big an area.