Glad you like RGL — thank you for the kind words.
I’ve been thinking about your last day ponderings, and have a few suggestions.
Firstly, Streatham is very child-friendly, and has good pubs and also pockets of interesting food (e.g. there’s a long-standing Somali community there, and you can find their food on Gleneagle Road just north of Streatham Station).
Secondly, if you stayed somewhere around the east part of the District Line, you could take the spring onion to a very good soft play area in Barking (The Idol), eat good food in East Ham or Upton Park (head north from the station in both cases), and pop into the traditional and atmospheric Black Lion pub in Plaistow (known for their beer, though, not their food).
Thirdly, there’s Deptford, which has a soft play on a par with The Idol (and cheaper too, in the Wavelengths leisure centre), several food options including Vietnamese, West African, and a sort of hipster collection of places in the yard by the station, and the Dog & Bell which is one of the best pubs in London.