Yes, get their accessory bars if you need to get them,
This Seattle parent mentioned difficulty finding compatible accessories from other brands that could fit the RadWagon cargo deck.
If you do not want bars but your wife would like more safety than a grab handle, consider the
aluminum accessory deck and Yepp EasyFit
adapter to fit the
Yepp Junior seat that fits a child from 5-9 years old and comes with bolt-on footpegs, it's probably a good investment to get the accessory deck for when you sell the bike because a future owner would then be able to fit Yepp child seats for younger and older children. The back of the Yepp Junior seat is cut out which
this reviewer said their child found uncomfortable. Alternatively the
Polisport Junior seat or the
Qibbel Junior seat do the same job but with a full seat back and do not need the accessory deck and adapter. Check the measurements with the manufacturer before you buy, but I suspect both will fit because the Polisport is designed to clamp onto racks up to 175mm wide and the Qibbel onto racks up to 180mm wide, the Radwagon deck is 6.75" (171mm wide).
This reviewer reported clamp-on seats scratch up the rack/frame paintwork so if that matters get the Yepp seat instead. Another rack seat for older children is the Bobike Junior but it does not fit onto the Radwagon deck only racks up to 160mm wide.