DDR-HP2 Wii friendship mode: Different levels for different players - how?

As a family we play Dance Dance Revolution Hottest Party 2 on the Nintendo Wii. It's the European edition (product code B002ATNS0S on the website of a popular online retailer).

We have 2 dance-mats (might get more in the future). We're really enjoying it - particularly 'friendship mode', because it allows us to work as a team.

So we've often got an adult playing on one mat and a child playing on the other mat. It would be really useful if we could have a different difficulty level for each of the players. Ideally in 'friendship mode' but it doesn't have to be - although we'd rather it wasn't a 'battle' kind of mode.

But I can't work out how to do this. Before the start of a game (when we're choosing a track and a difficultly level), if player one presses up/down then it changes the difficulty level for both players. If player two presses up/down then it changes the difficulty level for both players.

So my question is: how do I change the difficulty level for each player individually?

I've already tried: going through all the different modes, looking in the options, reading the manual, and looking online. I can't find anything.

I realise that in 'friendship mode' it doesn't matter if one of the players misses some of the arrows, but we'd like to have an easier set of arrows for one of the players, otherwise it's confusing for our youngest. Doesn't have to be 'friendship mode', that's just a preference.

I feel like I'm missing something obvious - sorry if I'm being stupid.