Caboose alternative

[vanakenm]

Hi!
My name is Martin, got a RadWagon 4 since a couple of years - 5000km, pretty happy with it.
My kids are now 5 & 9 (even if on the small size), and the caboose start to be inconvenient (notably complicated to park in bike space).

Does anyone use an alternative? Kids are too big for the Yepp. I'm thinking running boards & deckhand, but seems the deckhand can only be attached to the seat, so it works only for the kid on the front, and I'd like the one on the back to be able to hold into something too.

Anyone has advice/opinion here? Thanks!