Summer baby clothes?
We do have a range of summer clothes for baby, just head to cottonlily.com and find what suits you.
Toddlers have buyable clothes, but babies don't. The only way to have a baby look as if its wearing clothes is to get a custom skin tone with clothes painted on the baby skin. However, they must inherit this skin from their parents and it means all babies from that family will have the same clothes. The website modthesims2 has some skintones with clothes painted on the baby skin, if you want to download them.
I washed my baby clothes along with the other household clothes (using fabric softener) and had no problems. Some babies, however, are highly sensitive or allergic to some laundry detergents, fabric softeners, etc. If your baby develops a rash, this may be the case and your pediatrician should offer some advice on laundering your baby's clothes.