We have 3 Dses aged 3, 6, 8 (2.4 yrs gap, 2.10 yrs gap). So far it is fairly easy going, trickier than it could be as middle one has SEN.
Cars - we have a Citroen Picasso with 2 Hbb & a 5-point harness. It's fine & cheap to run, big boot too (fits buggy plus 5 small suitcases easily).
Holidays- so far we've only been self-catering but we prefer that anyway. Just had a week in a villa in Portugal in school easter hols for about £1300 Inc flights & car hire. Go to France during October half term for £350 ferry & Eurocamp static home. The trick is to go during school holidays other than the big summer one.
Childcare we have found fine as both sets of GPS willing to babysit at weekends plus 1 set of close friends.
Activities are very expensive! If each DC does 2 clubs each at £40 per term, that's £120 per term. Ds2 gers dla so that pays for his, ditto days out (gets a free carer to lots of places).
Clothes not so bad, we hand down between the 3 boys, only really trousers & shoes that need replacing.
One-to-one time is tricky but I've started getting DH to stay with 2 while I take 1 shopping & Costa in Tesco.
Playdates can be tricky as bigger children don't really want little ones hanging around. But we manage.
I did have 3 of 5 & under at one point & found parks difficult once Ds3 was on the move, as they all went in different directions. But that only lasted for a year & now they all play together & look after each other.
I don't work, partly due to having 3 DC & partly due to 1 having SEN. I will try to work once ds3 at school but will have to be self-employed so I can attend all necessary appointments & events.