Will share my thoughts having lived and/or worked in many different parts of London and Herts over the years (SE Lon, SW Lon, NE Lon, Hitchin, Harpenden, St Albans, Hemel). I'm a Dad by the way (if that's ok), married, with a 4 nearly 5 year old boy
Recently moved from St Albans (small 3 bed terraced, tiny garden, but not far from St Albans town) to Leverstock Green area of Hemel (4-5 bed detached, nice house with big garden
Pros: Son loves having more space both in the house and in the garden. Great to have friends round (from Herts or N.London mainly) and actually have space to entertain properly. Generally happy with the decision. Nice area, easy drives to St Albans, Watford, Berkhamstead, and various other bits of Herts/Beds/Bucks. Good train service (either from Apsley station or from St Albans) to London. Many weekends we'll go to London, eg Bloomsbury, South Bank, Soho. Taxi to Luton airport in 15 minutes when it's quiet. Short walk to village shops.
Cons: Hemel town centre itself is not great, sadly, so much potential but not sure why it's not achieving it. Leverstock Green very quiet if you're used to London life on your doorstep. Have to drive to anything more than village shops. Also not sure about state schools , our son is in private education.
Also:
Berkhamsted or St Albans are probably the best places to live in the sort of area
you seem to be considering, but also the most expensive.
Have you thought out of interest of areas like Bushey, Watford, Radlett, or are you needing to be more towards the West?