how to play with them indoors on a rainy day?

When I cared for a highly energetic young dog who needed a ton of exercise, I utilized soft toys and the many stairs in his house to either roll a soft indoor ball down the stairs (which he'd chase down, retrieve, bring to me, and repeat) or drop a soft toy from the landing above to the landing at the bottom and let him run up&down the flights of stairs to get it and bring it to me and repeat again and again.

It may be a bit tougher to play with all five in a safe way. If more than one dog really needed to expend energy, I'd likely use multiple indoor toys and roll/throw enough of them that each dog could easily chase & play with at least two at a time perhaps in slightly different directions & timing (to prevent squabbles) and definitely keep all the action where I could observe it.