Milk issue first. I believe as long as the kids eat a relatively balanced diet, no milk is required. You can get calcium from other sources. But, I might suggest a vitamin gummi daily to supplement.

When we were that age, my parents would allow us to be by ourselves but the rule was always. "no other kids allowed in the home". We could have kids over to play OUTSIDE only if our parents weren't there.

I honestly would play the going to other kid's houses on a case by case basis. I wouldn't let them free range that, but if they clear it in advance and you can talk to the parents (which would allow you to give them the power to evict SS when he becomes a pain).

The pool is a bit complex. Theoretically, if they are able to practice good water safety, they should probably be ok with using the pool. BUT.. other kids? maybe not the best idea to have unsupervised in the pool.

I might suggest you invest in some security web-cams. Maybe one directed at the pool area...another in the living room/great room. You can access them remotely. You also might want to set up a schedule of "check in" calls (via a facetime app) where they have to give you proof of life so to speak.

IMHO...

- I would not let them play outside this summer, since it's the first summer they're staying at your house alone I'd have them stay inside only to see how it goes first. Unless there is a pre-planned activity with a friend etc.

- I would absolutely NOT let them swim. Yes they could be great swimmers and be fine, but my skids are of a similar age and although they can be very responsible, when they get in disagreements they forget certain "responsibilities" so what happens if one kid is done swimming but the other one wants to continue? My skids would get pissed and one would end up breaking the rule of always swim together, and stay in the pool by themselves. Or if they're horseplaying and joking around and one of them hits their head on the edge of the pool and needs to go to the hospital. Pools can be very dangerous in A LOT of different ways, not just bad swimmers drowning, and I don't know that these kids are old enough be be able to handle a real emergency by themselves.

- As far as the milk goes, I'd say 1-2 glasses a day is pretty standard, but if he won't drink milk, try to supplement with other high calcium foods (cheese, yogurt, calcium enriched orange juice, etc) or add a daily vitamin to his routine.

Overall for the kids boredom, if they're anything like my skids, they'll sleep until 11am, get up and eat something and then play video games for the rest of the day. We simply make them get off once we get home around 5pm so they're not on it all day. Maybe you could do that, and then they can swim and be more active in the evenings once you/DH are home to supervise.

I wish DH could leave the skids at home by themselves but they just aren't mature enough to stay home by themselves. We never leave them home alone even if we go to the store. You are luck Ninji that you don't have to pay for a babysitter LOL. As far as the pool goes me personally I wouldn't want them to swim alone.

I would not say anything, not my kids and not my problem, DH can think of ways for them to entertain themselves.

SS love reading - good if he wants to do that the whole day so be it...

Their ages and staying alone, swimming or not - no problem I was much younger..
My parents handed our chores and we had to to them, if not you got punished, and having friends over to swim was a big NO...... friends could only come for a swim when my parents where at home...

If we wanted to hang with friends, we could leave after our chores where done and we had to be at home 5pm....

They don't need milk. There is more calcium in broccoli than in milk.

Have a list of things to do around the house - could be simple, things like disinfecting doorknobs and dusting picture frames... could be useless (to them) - like taking out all cutlery from drawer, cleaning drawer, organizing all cutlery...

here are some things I get my kids to do in the summertime. They can do it whenever they want during the day, but it MUST be done by the time I get home.

-pulling out stuff from drawers, cleaning drawers, reorganizing stuff in drawer (in the past, they've also made "boxes" out of recycled cereal boxes to help them "organize"... they're stillin the drawers, 2 years later...)
-turning all cans/boxes facing out in pantry
-making sure all bags in pantry are properly clipped and upright
-pulling all hair out of brushes/combs/elastics/drains
-restocking salt/pepper dispensers & sugar container if you have one
-braiding a grocery bag rug
-weeding a section of lawn/garden
-wash garage door
-wash extra vehicle
-sweep deck
-sweep porch
-weed whack around garden stones
-make grocery lists
-make a picnic dinner (on a friday) complete with drinks, cutlery, and games, so that when we're all home we can just go to the park and enjoy
-set up a tent (there's actually one in my yard right this moment, my girls slept in it Sunday night)
-make birdfeeders
-paint rocks Glow in the dark
-clean grout from between tiles
-clean duct grates
-take squeegee to stairs for cat fur
-draw "hypothetical" room decor designs if we were going to redecorate
-draw "hypothetical" house designs if we were to win a bunch of money and get a new home
-and of course regular chores like vacuum, sweeping, mopping, mirrors, dusting, bathrooms, cat litter... and clean the kitchen after making breakfast/lunch...