Totally like being in an episode of Outnumbered!! Funny that you too associate with that programme, grumpysquash 
We have boy boy girl and the relationships are fascinating. Age gap between eldest and youngest is 9 yrs and he is like an extra parent to her, but a fun one that has time to spend hours reading to her or cuddled up on the sofa with her! Age gap between the two youngest is 3 years and they are like close siblings, playing together all the time. Things may change as they get older but for now it's nice. The middle one is...well, very 'middle child' and needy/competitive in many ways, but who'll ever know if that is due to circumstance or personality.
Gender is no issue so far. DD just wants to copy the boys and play their games.
Life is noisy. And a carefully planned military operation!
A shower without being hassled is a treat!
I never take them with me to supermarkets if I can help it!
We don't go on holidays (cost) but on the plus side they are easily pleased - a ramble in the woods to build shelters and eat picnic is a fab day out for them, for example.
Space outdoors is a must - put them outside in the garden after meals to run around and make some noise before bed.
Highly recommend three, can't imagine life before it!!