Hi Soph,

We did it in 2005 but ours were older and we went in the night. We drove from Sydney to Melbourne and then caught the ship across. The kids loved it. I thought it was pretty good too. I was 11 weeks pg with Ivy and Noah at the time and wasn't feeling the best but had no issues with sickness etc.
There isn't alot to do for children - a little playground area and a movie room, an obsevation deck, that's about it, from memory. Are you able to go overnight or is the daytime the only available option (I know they don't travel through the night for some months) because for us, it worked really well that way. We got on, had tea and then after a walk around and some settling in time we went to our cabins and to bed, woke up in the morning and were off the boat in time for brekky.

ETA, not sure but think Fi has just done it with her littlies