I hope you take it in a little bit that your DH is thinking, having the best summer ever, yes, although spending at every opportunity can't be an option. Your son is a blessing, you're going to have a nightmare on your hands, if DS gets the same outlook as you. That money is needed for happiness.
Most people, as it's been said, are always a pay cheque or two away from being homeless.
What if there is a time when no money is coming, especially depending on how long you're on maternity leave.
When I first got pregnant there were no perceived worries, it was going to be amazing. Then I got really ill, even with family help the care I needed plus DC needed looking after, so two incomes gone in a click of a finger. Never used the benefits system before, so DH couldn't get Income Support as he didn't get carers allowance, he also couldn't get Job Seekers Allowance as he wasn't able to work. The staff were really supportive, To get everything sorted took several months.
Our hefty savings dwindled down. At times there was concern if everything could go out bill wise. That was sticking to a strict budget for food shopping, being the first of their generation in both families, DC had most clothes sorted by family's& close friends.
Most people call their savings their 'rainy day fund' for a reason.
One last thing, I'm sure your DH would have loved dinner by the river, he also understood that you'd be out prior, it'd be better next week or another time. You need to organise a budget and split it into subsections. Once you've blown a part of said budget, it makes sense even if DH wasn't a contractor, I'm sure he'd be the same, wanting to protect his family.
You really need to have an honest discussion, otherwise resentment will build. You really need to be on the same page when it comes to financial affairs, just like you would have before conceiving DS.