hazlinh - I'm really sorry to hear your family is going through this, - its a difficult thing to cope with. My Dad has had alzheimers for about 8 years now, - it's now fairly advanced. He is on aricept, and early on it did seem to delay the progress of the disease, although of course it can't stop it.
Once your dad has a confirmed diagnosis, he will be eligible for help from social services etc. and your mum should be able to get some help (my dad has people in to wash and dress him every day)
Initially he went to a memory clinic - where keyworkers did activities with a small group of people with dementia, memory quizzes, craft stuff linked to helping memory, generally helping them to try to use their memories.
Once he'd been there a while, he was assessed as being able to benefit from going to a day centre, where he now goes 3 times a week. Again they do loads of different activities , some physical - (mini golf, quoits, throwing balloons around) some mental (quizzes, games , bingo etc.), they also give him a shower at the day centre. Despite a lots of initial protest, he quite enjoys it now.
My mum goes to a support group for carers of people with alzheimers, - they all meet up for coffee they have speakers visit, they get help with applying for benefits, and they occasionally go on outings to get a bit of a break.
I think what I'm trying to say is that you will probably find there is quite a lot out there in the way of activities that may help your dad, but in our experience you have to be fairly pro active and ask what there is, - they don't exactly advertise the help.
If you have any questions I might be able to help with, - just ask 