Car seat for 3yo

[DadAndy]

DS1 has just turned 3, and he's about 16kg

Is he big enough to move to a Group 2 seat, as I've read they are for 4yo+, but they also say 15kg+?

He's in a Group 1 now, but DS2 needs that as he's outgrown his Group 0 seat

Obviously if he's not big enough, we'll get another Group 1, but I'd rather not have to buy something we'll replace in a few months; especially as we don't own a car, so this is only for occasional rentals

I would get one with a impact cushion child that way you won't have to worry about him not getting his arm out. To go in one without a impact cushion he needs to be also tall enough and sensible enough to sit still.

There are other threads listing them

hmmmm...he can stay in his group 1 untill he is 18kg or his eyes are level with the top of the seat, is DS2 in a group 0 or 0+? he can stay in that untill:
group 0 - 10kg
0+ - 13kg or top of head level with top of seat

If ds2 has outgrown 0/0+ seat then maybe get a group 1-2-3 for ds1? that way he can stay harnessed untill 18kg then the seat converts to a high back booster.

EG-
Britax Evolva
Graco Nautilus
Cybex/Kiddy impact shield seats

If you have different rental cars you may have a problem with seat belt length on the evolva or impact shield seats, but the graco might provide problems with buckle crunch depending on the car!!!