Hi Cindy. We also field 3 courts of dbls and 2 singles. Every team I have played on has 2-3 singles players and maybe one person who has the skills to play both singles and doubles.
Odds are that a doubles specialist will not be terribly successful at singles without working on the skills and strategies that are specific to singles. If a player is reasonably athletic, has a consistent serve and reliable groundstrokes, then they can probably apply a few singles strategies and be successful.
Perhaps you can put together a few drills in which the pros work specifically on singles strategies. Things involving lateral baseline movement, approach shots, court coverage, etc. You and your team mates might be surprised who emerges as potential singles players.
You also might be able to form an informal singles ladder within your team to give people an opportunity to try singles. You don't have to play sets. You can perhaps have a few courts of singles and have each court play 6-8 games then switch.
It has always been most difficult for us to field singles courts, so it is in your best interest to encourage as many folks as possible to at least try singles.