We had an au pair for 4 years while DH spent 2 consecutive weeks away and 2 consecutive weeks at home, on a regular enough pattern (in that, sometimes his trips were longer but generally left home Sunday lunchtime and got home mid-morning Saturday 2 weeks later for that whole period, so only 1 full weekend at home a month, and having to still fit in visits "down home" to DPs and DPILs on some sort of frequent basis). That helped as AP brought DD to school and collected her from afterschool club in crèche/later on from afterschool club in school a few evenings a week.
Creche had afterschool activities (mostly optional for an extra fee). School also has a very good programme of afterschool activities run by PTA, and afterschool club also run by PTA means DD can do activities in school and go to afterschool until 6pm - and I get there at roughly 5.45. So she's tried a range of sports, chess club, French, guitar etc (things like drama, musical theatre, book club, debating, art, gardening, lego, and good few sports are all options).
DD learned to swim at lessons in another school - started Saturday mornings, had to move to 6pm class one mid-week evening when she progressed to level 4 (which we could JUST get to), and AP used to do it by taxi for another year when we had to go to an earlier slot. But as it was getting unsustainable, was just the point where DD was a confident swimmer so we were happy to drop it.
She does sports at weekends - hockey and gaelic games. But as gaelic has needed midweek training since last year, we've been slowly dropping back on that. We could make it but she's exhausted midweek.
Scouts on Saturday mornings, sailing Saturday afternoons (right beside each other), computers Sunday mornings before hockey (well - we did that for 2 years but she knew lots were on waiting lists and was happy to drop that this term voluntarily). I can get her to all those easily enough. And she wants to be busy.
I am a leader in Scouts, and used to play hockey so practice that with her. DH enjoys practicing gaelic with her.
Holidays are interesting. Sailing school does full days (9-5), and the local Uni has sports camps with pre/post care from 8.30-5. DD loves the sailing so does 3 weeks (DH drops and does a lot of collections those weeks - childminder who does the 1 hour in the mornings in school terms is happy to do either/both if DH has to travel). She wants to do the sports camp which is near my office, so commutes with me and I do that week. A week with Granny in the country. And we usually manage to find another camp with long days somewhere, or the minder can do afternoons for us, for the other week.
And sailing for most of the holidays during the school year except Christmas - which we tend to be off ourselves.
But all that does take thinking ahead and finding things that DD will be interested enough in and that there are spaces in.