I would ideally suggest rear facing as well. But, if you are not going to do that, I would look at:
* Britax Frontier85 - tallest top slots and weight limit so he can be safel harnessed until he is old enough and mature enough to sit properly in a booster (which the FR85 turns into a nice high back booster, and it doesn't expire until 9 yrs from DOM, so it would last a long time). While it is upright, the headwings can make a nice sleeping surface
* Graco Nautilus - it would last a long time, though not as long in the harness as the FR85. It does have some recline FF but tends to cause headslump issues for some kids, even older ones, so I would keep that in mind.
* First Years True Fit - as a convertible to be used only FF, I would choose this one over the MyRide because it has taller top slots and therefore would last longer. It doesn't have as much recline when FF as the MyRide, but does still give some natural recline.
For RF, I would look at the Radian models which RF to 45lbs and the Complete Air, which RF to 40lbs. Both would offer more growing room by height over the MyRide.