I think you can be more frugal without feeling like you're missing out on life though... Aside from the obvious house/car/child care situations. If they can be overcome, then there are options -
Spacing children out definitely helps with costs - age of needing childcare, clubs, socialising, driving lessons etc.
How you holiday - would you be happy piling in the car and driving to France and renting a big house? Or do you have your hearts set on two weeks AI in Gran Canaria every single year?
When you have weekends and days out, do you HAVE to go out for lunch, cakes, coffee, ice creams etc, or could you pop to the bakery for a cake and the Co op for a multi pack of ice creams?
Once you've bought the cot/baby furniture/jumperoo/pushchair etc, you can keep them and use them again for the next baby. Clothes can sometimes be saved and passed down, particularly baby clothes when they're growing so fast.
When you cook and shop, do you plan meals, do you have to have an entire chicken breast each, or could you chop less up and bulk it out with vegetables etc. Can you all have packed lunches instead of cafeteria/school meals? Do you meal plan to reduce waste?
All this things and loads more, soon adds up. Children are expensive, but every day life doesn't have to be if you change the way you think. We have four children and happily live like this, whilst still affording a nice life (to us - I don't wear Ralph Lauren admittedly), but the children don't go without, they get residential school trips, after school clubs, Clarks shoes, nice clothes and a holiday. And they have a selection of live in play mates to enjoy every single day.