The nights are just too short. How late to play with friends on a school night?

How late to let kids play with a friend on a school night? Our kids are 9,7,7 in 4th and 1st grade. Evenings are just too tight and that is without sports or extra curriculars.

We get home around 4, unwind for a bit and do a bit of homework. If not a ton of homework and no mega chores they can romp until 6ish usually. Dinner can be anywhere from 5 to 7pm. Kids get a bath or hosed down at somewhat regular intervals. Book time is 7ish, at least 25 to 30 minutes as many times a week as we can pull it off. Find pm jammies, place shoes where there is a chance of locating them in the morning, if we are lucky pick clothes for the next. day, brush teeth try to have screen off 15-30 minutes before bed. Not always so lucky, sometimes that last 15 minutes of negotiated tv is key for moving them towards bed. Try for lights out at 8:30 with chit chat snuggle and tuck. Then repeat for unit 1 who gets about 45 minutes more based on age.

One of the neighborhood kids came over at 6:15. To me that was too late to start playing. But I wanted to ask as a sanity check. Mine hardly use their outdoor play stuff unless other kids are around. It just seems that the evenings are too tight for that. On the other hand it is better than TV and keeps them moving. Said kid has only showed up once or twice at that time so I haven't said anything to parents yet. Is letting them play outside longer on a school night advisable? To me it feels like it would upset the balance of the force.

We are in year round school, tracked in for 9 weeks, out for 3 weeks. Repeat.