Kate wrote:

time. DD will be 5 and DS will be 2 in August.

DD is at school so it's only between 3.15 and 7 pm when DS goes to bed
but it seems an awful long time when all they are doing is annoying each
other. DD gets home from school tired. She used to say "mummy I want to
do something with you but without DS" but has now realised this is
impossible (except on Fridays when he is at nursery and I make sure we
do something together then). She likes long, involved imaginative games
with her castle or dolls house or playmobil or all 3 combined. He likes
running around and shouting. It's not a good combination :-). She takes
her things away from him, he hits her, she pushes him over... If she
watches TV, he turns it off to get her attention, she pushes him away,
he bites her... Recently it's ended up with her going to play in her
bedroom and me having to keep DS downstairs with me, which makes him
cross because he wants to follow her around and do everything she's doing.

So I've been trying to find things we can all do together that will keep
both of them happy. So far I've found music is good, dancing to it or
playing instruments (if I can find two absolutely identical). Also DD
teaching DS songs and action rhymes or action games like "Simon says".
Ball games are sometimes OK but DD gets cross because DS doesn't follow
her rules and take turns.

Any other ideas or are they just going to be totally incompatible for life?

I don't see why you would have to create so much
together time. My inclination would be to try to jiggle
his sleep times so that she has a little time when she
gets home from school to reconnect with you without him,
and then some time after his bedtime to play in a more
extended way with you. Is Dad around any of this time
so you can divide and conquer a bit? Then, it's perfectly
reasonable for her to play on her own for a bit while you
keep DS out of her hair. He has to learn to do that--it's
not unreasonable of you or her to require it of him. It's
also reasonable for your daughter to learn to be a bit
forgiving that he doesn't always understand or play by
all the rules at less than 2 years old. On the
weekends, arrange some one-on-one time with each of them.
When you have multiple kids, I think you have to
find some balance of play alone time, play together time,
family time, and one-on-one time with each parent. I wouldn't
attempt to maximize your family time at the expense of all
the others. I'd just shoot for a balance. I doubt you will
find a terribly long list of activities that are absolutely
fabulous for both an almost 5yo and an almost 2yo. They
each deserve *some* time tailored towards their specific
needs. You're hamstrung a bit by the toddler requiring
so much hands-on care just from a safety perspective, but
that will get better fairly rapidly. If your daughter knows
when she can count on having your undivided attention for
play appropriate to her age, I suspect she'll cut you some
more slack on the time that she knows you have to spend
playing all together.

Best wishes,
Ericka