As for age and health, I'm 57 and DW is 49. I'm 5'11" and DW is 5'7".
We're both larger than we should be. Crawling into the cabover bed is easy enough. Getting out entails either getting on hands and knees and crawling backwards or sliding yourself. With the extra headroom in the Host, it's much easier than it was in my non-basement model Lance. The standing area height of the Host and my older Lance was about the same, but because the floor on the Lance was down in the truck bed and the Host is on top of the bed rails, the overall height is much higher on the Host. Downside is that the Host is really tall. Upside is that the cabover on the Host has a lot higher ceiling.
If you're not sure what it will be like living with a camper, try getting on and off your current bed from the foot rather than the sides.
As for making it, that's no big deal. Just crawl in, start with the top two corners, then do the bottom corners. Again, it's much easier to crawl on the bed with the extra headroom in the Host.
Campers with a front bath that blocks access to one side of the bed would be much more difficult to deal with.
At home, we have a split king adjustable bed, and ordered the Host with a king mattress and am thinking of changing it to an adjustable split king as well. I couldn't do an adjustable in the Lance as it would have raised the height of the mattress and made it too claustrophobic.