A Gruffalo is a creature you have tea with, and that's good in my book.
I don't remember worrying about bumps, but like the Clariflies we had a Hamax (I wasn't aware this made a difference, it was simply what was available at the time and place) and he was bigger when we started anyway. I do remember riding through puddles being the funnest thing ever. And being pushed in the back, "helpfully", whenever we went uphill.
The pictures, I need not say, are delightful.
Oh, I've just this millisecond had an idea; it would be especially adaptable to a Circe, I think, but a pair of solos could do it too. You need two baby seats, one baby and one of those village hall urns full of tea. And two mugs. I'm sure you get the idea already. Perhaps you need a method of preventing baby scaldings too. Perhaps tell the baby there's a Gruffalo in the urn?