thanks for moving it. I still have the 4 year old who is 38 inches? My 7 year old is 48 inches.
At 38 inches your child can:
Go on all the harbor boats (my kid is not that into this, your kid might be)
explore the fortress (I had an adult friend who thought this was amazing, I wasn't feeling it. She claimed kids would love it. I am less sure my kid will like it.)
Turtle Talk with Crush (a 3D movie that can respond to viewers)
A railway
more boats
Toy Story Mania (this is also in the USA both CA and FL, it's insanely popular)
Aquatopia (sort of like bumper boats... I did this one, it's cute but the line can get long)
Nemo (This is new and replacing Stormrider which was a motion simulator ride. They say kids over 3 can ride it, and I think it shouldn't be too scary? Long lines, because new and only in Disney Sea.)
The carousel
A Sinbad ride (it looks slow?)
Flying carpets (it's the Dumbo ride with carpets)
Magic Lamp Theatre (Aladdin in Japanese)
Ariel's Playground
Jumpin Jellyfish (they have this in CA)
Scuttle's Scooters (this is a kiddie ride)
Flounder's Fish coaster (a kiddie coaster)
Blowfish race (another kiddie ride)
Mermaid Lagoon (an Ariel show done in Japanese)
The Whirlpool (think tea cup rides)
20,000 Leagues Under the Sea
Your taller child can ride everything
Journey to the Center of the Earth starts slow and then becomes a coaster (I loved it.)
Raging Spirits (is a real looping coaster)
Indiana Jones Ride (I didn't ride but did in CA and I think it could scare some kids)
Tower of Terror (My daughter did this in FL and was scared out of her wits. It's a real free-fall ride.)
So there is a Summary for DisneySea.