You can order a smaller amount of rice with your sushi.
ーYou can choose to have less rice with your sushi.
「シャリ少なめを選べる」
to choose で「選ぶ」
less rice with your sushi で「シャリ少なめ」
ーYou can order a smaller amount of rice with your sushi.
「シャリ少なめを注文できる」
to order で「注文する」
a smaller amount of rice with your sushi で「シャリ少なめ」
ご参考まで!
You can choose less rice.
You can get it with less rice.
You can choose a smaller rice portion.
You can ask for less rice.
They offer a “less rice” option.
「しゃり少な目」は、英語だとそのまま “small rice” ではなく、「ご飯(rice)の量を少なめにする」という言い方にすると自然です。