Don't bring him in August. He will be mostly confined to your home and shopping malls. The weather is miserable hot + high humidity so walking is a chore even when the sun goes down.
I would recommend waiting until late September/early October when the humidity is starting to break.
HTH
I'm from the UK and my parents visit regularly and never have any issues that you've mentioned below. Like your dad, they're both fit and well, exercise regularly and their GP is more than happy for them to enjoy a holiday in the sun.
My dad turned 80 this year and his most recent trip was a month from mid March-April. He loved every second as usual! He's also on Warfarin and had no issues.
I get their visas via Al Maha meet and greet service at the airport. I'd strongly recommend that you use these agents to meet your dad from the plane and whisk him through immigration to you. I wouldn't have my parents arrive in Doha any other way. Real peace of mind for both you and him.
However I would caution you on your proposed timing. End of July really would be too much for him. By mid April my dad was starting to find the heat uncomfortable and he is well used to high temperatures (him and mum go to Greece in July each year). If you want him to truly enjoy his time in Doha, then wait until late September at the earliest.
I hope you have a lovely time together!
.jpg?itok=4utim_xh "You Can Now Apply For an Exceptional Entry Permit on the Qatar Portal")
.jpg?itok=OdfWVChW "How Qatar Students Will Return to School From September 1")
.png?itok=3d-9ov-m "Distance learning at Hamilton International School")
.jpg?itok=huYiXiog "You Can Now Apply For an Exceptional Entry Permit on the Qatar Portal")
.jpg?itok=WvzOqcwJ "How Qatar Students Will Return to School From September 1")
.png?itok=6xLVeUta "Distance learning at Hamilton International School")
