DC for Balance on Icy Logs?

[Palanan]

I’m planning an encounter on a broad, heaving tangle of logs in an icy river. The logs will be wedged in place, but they’ll be shifting slightly from moment to moment, and they’ll be covered in a thin skin of ice.

I’m planning on Balance checks for every round in combat, for the party and foes alike. What would be the appropriate DC for a situation like this?

[Albions_Angel]

DC 5 to stay standing or to single move. Roll again for a second move. Maybe think about allowing them to cancel the move or spend the round balancing rather than just have them fall over. Being prone is annoying if it happens every round.
DC 10 or flatfooted.

Its not a sheet of ice, so its probably quite easy to stand on or to move carefully. The rocking logs probably bring that back up to a 5.
5 ranks in balance generally means you can not be flat footed on uneven surfaces. So +5 onto the base DC seems right.

Trips should be handled at a -2 minimum, maybe -4 to the tripee.
If a player has the ability to freeze an area solid, let them. Creative solutions would be good in this scenario.

This should be a minor chance. If everyone, enemies and players, are falling over, its no fun at all.

[Malimar]

DC 10 or flatfooted.
RAW, by my understanding: unless you have 5 ranks in Balance, then every round you're Balancing you're flat-footed.

You could do it Albions_Angel's way (honestly it's quite possibly better in this situation), but it would certainly be an interesting change-up for everybody to be flat-footed every round. Rogues and iaijutsuers would like it, anybody who likes to make AoOs wouldn't (unless they have Combat Reflexes).

[Albions_Angel]

Raw you are right. But I wanted to go a little further. In this situation, the ground isnt just difficult to stand on, its actively moving. I dont feel its enough to be sure footed (5 ranks in balance). You need to actively be shifting your feet every round. As thats a more active task, a + to the DC made more sense to me than a passive "Im good at standing on things" kinda thing. The DC is still low enough that if they are level 5, they can probably ignore it (5-8 ranks, 2-4 bonus, minimum 1 roll, so at min its an 8). But its enough that both they and the enemy should end up flat footed once or twice. Sure, rogues should love it, but then the rogue has to make the check (all be it auto-succeed unless they paid the balance tax) just to not have to spend a round balancing and actually attack.

You could have the whole thing be just flat footed, but all that does is make combat simultaneously easier AND more deadly. At least with the flat-footed roll, it feels like you are rolling for more than "do I fall over".