I have the same tension of family function vs growing things in my garden, but our secret weapon is the woods and park just over the back fence! I think we have enough space for games of catch and quoits, short egg and spoon races, perhaps miniature croquet and that sort of thing, but for anything football-like we'd go off to the park. We can fit a paddling pool (if it was ever warm enough!!) but I don't plan to introduce a sandpit, oh no.
Am going to move the whirligig this year to the edge of the lawn next to the deck, so that I can put things on the line without walking on the grass (e.g. if it has just stopped raining, or if I can't be bothered finding shoes).
I planted a couple of hellebores last year that a friend gave me. One is taller than I expected and has a lovely structural white flower now. The other doesn't have a flower head (well when I looked at the weekend it didn't) so perhaps it is too immature - my friend did say that they were divisions/self-seeded.
We have a grass verge out the front of our house that I'd like to strew with wildflowers but I would be worried the council will just come by and mow it. Wonder if I could obstruct it just enough to make it difficult to mow? It would definitely not be a safety issue to let it grow long - it is a verge between the parking layby and the pavement, not a direct roadside verge. Maybe I should ask more officially.
I'd happily move shrubs now - sheltered garden but not immune to frosts. Possibly give them a haircut and a root trim too - they'll sulk for a while but be stronger in the long term. Have a look on the RHS advice pages for the specific plant - might tell you exactly when to move it.