The only way I see it working is if you have a multiple of 4 people (half adults and half children). Then you can use the schedules in the downloadable
Excel spreadsheet attached to this thread - you must be logged in to the forum to see the paperclip download icon. The schedules need to be adjusted by shifting the order of the columns in each foursome, keep 'a' for adult and change 'b' to 'c' for child. So for 20 players the converted schedule would be:
Game 1 Game 2 Game 3 Game 4 Game 5
Round 1 (a1 c1 v a6 c6) (a5 c5 v a10 c10) (a4 c4 v a9 c9) (a3 c3 v a8 c8) (a2 c2 v a7 c7)
Round 2 (a5 c3 v a9 c7) (a4 c2 v a8 c6) (a3 c1 v a7 c10) (a2 c5 v a6 c9) (a1 c4 v a10 c8)
Round 3 (a4 c5 v a7 c8) (a3 c4 v a6 c7) (a2 c3 v a10 c6) (a1 c2 v a9 c10) (a5 c1 v a8 c9)
Round 4 (a3 c2 v a10 c9) (a2 c1 v a9 c8) (a1 c5 v a8 c7) (a5 c4 v a7 c6) (a4 c3 v a6 c10)
Round 5 (a2 c4 v a8 c10) (a1 c3 v a7 c9) (a5 c2 v a6 c8) (a4 c1 v a10 c7) (a3 c5 v a9 c6)
This is also a team competition between Team A (a1-a5 & c1-c5) and Team B (a6-a10 & c6-c10), but you could choose not to tell them.