The Sims Castaway Stories (Wii) is rated T for Teen and does not contain explicit sexual content. "Making out" / "WooHoo" is represented by fully clothed Sims kissing, hugging, and disappearing under covers with heart/star particle effects—then a relationship boost.
The game focuses on relationship building, storytelling, and survival tasks (fishing, crafting, exploring). Romance is a sweet, cartoonish subplot—not graphic. Perfectly appropriate for its Teen rating.
If you're looking for adult mods—none exist for Wii (closed platform). PC Sims 2/3/4 have adult custom content, but that's a different ecosystem.