Wait until your child sits steadily with full neck control, usually around 9 to...

https://www.yankee-bookmarkings.win/wait-for-strong-neck-control-and-independent-sitting-usually-by-age-one-front

Wait until your child sits steadily with full neck control, usually around 9 to 12 months. Front seats keep them engaged, while rear seats offer great stability. Trailers provide a cozy, shaded space for naps