My own view is that there should be a healthy balance of activities, some simple, some more exciting and that they should be appropriate to the majority.
Mum's CH has always had an extremely ambitious programme. It looks immensely appealing when you are first considering CH's - but in reality it's for the few, not the many. It tends to be the same able and compliant residents that are taken on the trips and the activities are aimed at the capable, with others just looking on, falling asleep or staring vacantly. Cynically I feel that these 'holiday camp' daily programmes are mainly for photo opps and amazing advertising copy and that simpler, more cost effective activities would be better and the money saved put into increased care.
Grumpy personal moan over!!
That said - I do think activities are very important for stimulation and social interaction, but staffing a group activity for different levels of dementia residents is difficult and a bit like herding cats! Small group activities of those with similar abilities are always going to be more effective.
IMHO the best activities have been - simple craft (where it really doesn't matter what the end result is or looks like and there are incentives on hand .... like chocolate!); Armchair exercises ; Anyone bringing animals is always popular - even just a couple of friendly dogs. Mum's CH regularly have a wonderful mobile petting zoo visit. They bring in all sorts of creatures that residents can hold and stroke; Performers, particularly of the 'sing a long' variety; Simple food prep and recipes (and eating the results afterwards!); Namaste care has recently been started for end stage residents, involving hand massage in a calming and peaceful room.
Personally, in the past I have used all sorts of stuff with Mum: Children's reusable sticker books with scenes and appropriate stickers to create a picture; sorting cut fabric squares into a patchwork pattern that I sewed together for her; I wrote on some cheap large plain wooden dice things like 'sing a song' ' make an animal noise' 'clap your hands 3 times' etc and we would roll them and follow the instruction; I got some coloured balls that were a bit like velcro and easily stuck together to make shapes; the marble game Kerr-plunk where you pull out straws and try to avoid the marbles escaping and helter skeltering down the tube; the Silk app on phone or tablet is brilliant to make spirograph type patterns just by touching the screen ... and the results can be printed; Mum also enjoyed sorting out things like buttons.
Outings do not have to be exotic - a walk round the block to look at neighbours' gardens - a quick trip to a shop to buy an ice cream - a picnic ...
There's a great book that I had intended to get, before Mum deteriorated so much, called 'The Activity Year Book .....' (I know I cannot recommend or give full title and details on here, but it's quite easy to find on a well known online shopping site) It's rather pricey, but has some fantastic ideas for all levels.