Hi Amanda, I believe that albino varieties of the African clawed frog (ACF) are probably more common in the UK pet-trade than natural coloured ones.
Also, as far as I'm aware, African Dwarf frogs (ADF) don't exist as albinos.

ADFs can be kept quite happily in numbers (depending on tank size) and can be kept with fish.....although feeding might be a problem as the fish and ADFs will compete for food and the frogs will probably lose out......I personally would go for a single species tank.

ACFs will require much more space per frog, hardier plants, and won't be ideal to share a tank with fish.....

I hope you and your family really enjoy your new pet