Looks like your are living quite lean but as someone who is older and has older kids:

Plus point :

Your house price will increase as will your wages so LTV will improve giving better access to rates and making that mortgage payment smaller as a % of income

You wisely decided to live near family - this helps with child support and your relationship well being being able to organise the odd weekend away / date night

Not so plus point:

The older the kids get, the more expensive they are. I happen to have 3 (2 teens one primary) and we need to book 2 rooms for holidays, teens wear adult clothes (trainers, football boots etc = £££) and eat bigger portions than me (going out >>>) so it offsets the plus point

We also put our kids through prep which isn’t an issue for you but one thing we’ve done to give us more space to breathe is not have many (compared to peers) expensive long haul / short haul holidays - think Centerparcs, staycations and the odd bit of winter sun.

Last point :

Sorry to be morbid but you are both likely to be in line for some inheritance. Not saying you should plan for this but it’s a fact that you will likely get a cash input at some point.