Out of curiosity, what tires are you running on your sienna. I’m assuming those are 16" rims.
Just your run-of-the-mill Continentals on factory 16" steelies. I like to run larger 235/65R16 - the stock 215/65R16s make the van look like a whale on rollerskates. I also replaced the entire suspension a few years ago to bring it back up to its original height and get some ride quality back.
I put zenna sport lines on my Sienna. They’re okay but despite being the correct load rating, I don’t trust them. Tempted to go to a light truck tire as ours is also pulls double duty as a work van.
As long as you don't exceed the load rating (very often), they'll be just fine. Keep them inflated at 36PSI. If you're still uncomfortable with it, there's nothing wrong with a good set of LT235/65R16 load range E tires. Just keep in mind that these tires are significantly heavier and ride much harder than the same size standard load tires. If you've got the 2GR-FE V6 (3.5L), it may not even notice the extra weight, but the 3MZ-FE (3.3L) will definitely notice; and your back will notice the ride quality. Still, it's up to you. Form after function, and all that.
Just something to keep in mind though, modern standard-load tires are fairly strong and are the standard tire on half-ton pickups.