You have to respect his wishes which it sounds like you are.
But if you think he may being overly polite and not wanting to put others out , you could reply
"Dear uncle
We would really like to visit you to stop in for an hour and half, just to reassure ourselves and see your lovely smile again, because you're family and really important to us. It's been too long.
We won't come if you really don't want a visit, but just wanted to check you're not saying not to bother if you are at all you're mistakenly worried about 'putting us out'.
We love you and would be delighted to see you again, can be just me (&DH/DW... no children..) if you'd prefer,
Of course we will respect your wishes, whatever they are,
love Tswift"
Then whatever your uncle says in reply, you'll have tried your best. Tbh if he can reply to emails, he's orientated and can make his own decisions.