mostly out of the drivers side but when we park on the side of the road i just un buckle him and tell him to go over to DDs side or he climbs through to the front passenger side.
when we had the capsule in or then rearward facing seat he could climb under it(through the foot well part) i always get him out first and tell him to either hold on to the rear passenger wheel or i get him to go and touch the wall(if parked at a building)

the only reason i didnt put capsule on the right hand sid ewas when putting them in you have to open the door completely you cant just sneak them in.iykwim

also DS is old enough that i can tell him to wait a moment if he need something where as if i had to hand dd her dummy i could do that...