It depends...what media are they currently growing in?
I have some 2 and 3 inch cattleya seedlings from Carter and Holmes and they are growing in an orchid bark mixture similar to that used for phalaenopsis; that is what most people prefer I think.
I have also seen cattleyas of all sizes potted in Aussie Gold Large/plastic pot, S/H/plastic pot, and NZsphag/clay pot. I have personally grown cattleya plants in all of these with success.
These last three methods require a change from the usual watering patterns etc used for bark mix.
Furthermore, I personally don't prefer S/H for seedlings as in my experience they dry out more quickly. I do however use S/H primarily for any of my catts when they get into a 4.5 inch pot size.
I would use the same mix they are currently in and just increase the pot size. If they are in plastic pots I would continue with plastic but I prefer clear pots. Do not overpot; only leave enought room for one or two years' growth.
Thus, you can keep the same watering, fertilizing, lighting etc. and they should continue to flourish