Buildersbum Zeus on the Loose is another fun Gamewright title that works well around that age. Otherwise our favourites are the ones you already have, as well as Duck Duck Bruce (but that is difficult to get hold of, and we played it more when the children were younger). We also have Too Many Monkeys and Moose in the House (wouldn't recommend either, no meaningful decisions) and Toss Your Cookies which hasn't caught anyone's interest either. We also had Frog Juice but gave it away as we didn't find it fun, but it tends to get good reviews so you might want to look that up. I bought BraveRats last Christmas (not Gamewright but Blue Orange games, a microgame by the same designer as Love Letter), but it didn't hit the sweet spot either.
Like you I am searching for a new small simple card game as a stocking filler for dd8 (who loves Love Letter, Sleeping Queens and Rat a Tat Cat but doesn't enjoy anything too complex.) I am considering Cardline Animals, but am not sure how small the actual box is. Otherwise, smallish card games (not Gamewright) we have had a lot of fun with over the past year are Cockroach Poker and Nobody But us Chickens, so those might be worth looking up.
We have also enjoyed Archaeology the Card Game and Monopoly Deal, both simple set collection card games in small boxes (although I think that there is a newer version of Archaeology that comes in a larger box).
Another small card game is Best Treehouse Ever. We opened it today but haven't quite figured out the scoring yet, so we haven't quite fallen for it yet. The artwork is lovely though!
As for Lost Cities recommended above, I love it but the rest of the family (dh, ds10 and dd8) find it too dry/abstract.