Dpup (8 months) is going to stay with my sisters family while we're on holiday - they have a 4 year old dog who my pup adores (she tolerates him doing things alongside her but doesn't actively play with him)
At the moment dpup has breakfast of kibble in a variety of treat-dispensing toys, a stuffed kong during the day and tea (the only meal he gets in his bowl) at about 6pm with some of his daily allowance of kibble used for training throughout the day. This seems to suit him perfectly - he's in fantastic condition, is a perfect weight and solid poos at predictable times.
My sister's dog has breakfast and tea both in her bowl and tea is about 3pm. She doesn't have many treats but the ones she has are much bigger (dpup has pea-sized bits of sausage or chicken or cheese or kibble)
Obviously I want to make things as easy as possible so what's the best way of keeping both dogs happy? I will be having her dog for a few days as well when we get back
Treat dispensing toys are unlikely to work in a multi dog situation unless your sister is able to separate them. Far too big a potential of squabbles. Your pup is also getting to an age where his puppy licence has expired and he might start experimenting with not backing down to older dogs.
I think your pup will have to fit around your sister's household routines, you can't dictate terms or be too proscriptive if you want her to dog sit! And it won't kill your pup to be fed differently for a couple of weeks.