Ian,
I had my first heart attack the Friday before Easter & the second one on April the 15th whilst waiting for an Angiogram, since coming out of hospital I've had to come to terms with the fact I can't do everything I used to! but it has not stopped me from vanning!!!! last week of June I drove down to the Dordogne, van in tow & had a wonderful 2 weeks away & am looking forward to going away 1st week of September.
As a result of the attack, we've not had many weekends away this year, mainly due to the fact that the medics tell you not to drive for 4 weeks after the attack & then recuperating for another 5 weeks.
But as long as your father in law is sensible & takes note of what his body is telling him, theres absolutely no reason why he shouldn't carry on vanning!
My van already had the motor mover fitted so if he hasn't got one, get one fitted as manouvering the van by hand is the biggest no no! as for filling the aquarol, if he's got the 40 litre one, fill it from the side cap & put the pump in that one as well, (just wedge the aquaroll with a couple of tapered wood wedges to stop it rolling away) saves having to up end it, the waste master already has wheels, so empty it daily rather than each time it fills up & likewise the toilet cassette, but I've taken to putting the cassette into the boot of the car & driving up to the emptying point, saves humping it there!
So the short (or in this case, long) answer is yes he can still carry on vanning!!!!!! just be sensible about it.