What class? Some don't need to be in pelhams, if child classes or novice classes, and a few others...
Some classes ideally should be pelham or double yes. If you got for pelham, it should be with 2 reins NOT roundings for the showring. Personally I'm not a fan of jointed pelhams as a rule, I feel the action of the cheeks are contradictary with a jointed mouthpiece a bit, but some horses do get on with them it seems. My first choice is usually a mullen mouth pelham, but have a play and see what works for her...
You should have a curb chain on for a show class: but that shouldn't come into effect when fitted properly if the rider leaves the curb rein alone, so I shouldn't worry. You can get elastic curb chains, which a lot of people use, and can be 'milder' than a chain. It's a really tough piece of elastic with only a tiny bit of stretch on it with usually 3 rings of chain either end to attach to the hooks of the bit as per normal. Used in the showring and not an issue
You should also use a lipstrap on a pelhap (or a double for that matter), to be correct too. It can look a bit complicated to put on, but when you look closely it's not too tricky and you'll get the hang of it.
A good way of introducing a rider to 2 reins if she's not used to it yet is just to add a second rein onto the snaffle if thats what currently ridden in. Will give the rider time to adjust to having 2 sets to cope with, without it having any effects on the horse if they get muddled (obviously this is training, not actually in the ring!).
On the note of reins: you'll probably like 2 different feeling reins - something obviously very different from one another so that if you drop your reins for any reason, or hold all in one hand for anything, you can pick the correct ones up in the right place easily. Personally I prefer the curb rein to be really thin as I find it much easier to slip and loosen the thin rein when suits, and then have a plaited normal width rein for my snaffle(or in a pelham, the snaffle position). However different people like different things: my mum prefers her snaffle to be the thin one. Doesn't matter, as long as you differentiate and use them accordingly
