I used to worry about the high bar on road bikes too because as a kid I always road step through bikes, but really it's not a big deal because you don't buy a bike that you cannot stand over. It occurred to me that I probably got the impression that it was an issue because when I road other peoples road bikes as a kid, they were always to big for me. But in the real world, when they fit you for a bike, you should be able to jump right off and have plenty of clearance. And also when you stop you lean to one side and you get even more clearance that way. :-)

I, personally, wouldn't want to do a half-century on a Trek 7000 series bike. I'm sure it's possible but the body position and the wide tires are really working against you over a long distance. And I find that shocks on the seat and fork distracting. But if that's the furthest that you will go, it should work.

You should probably test ride the Trek FX series, the Specialized, and the Giant Dash series just to see if the flat bar road type bikes really feel all that different from the 7000 series for you. You might be surprised by how comfortable they are in the body position. You really aren't (don't have to be) as hunched over as you would be on a road bike where you have to go into the drops to pull the brake levers. The height of the handle bars can generally be adjusted to give you the body position that you want.

Good luck!