Just an opinion, for what its worth (from someone who has used dog walkers and dog daycare a lot over the years).
When you are able to re-open I would be tempted to see how your customers react before incentives to get them back.
You may find that they will be so appreciative of the opportunity to have their dogs active and fulfilled again that they come back as soon as restrictions are lifted.
I would reach out to your customers and let them know that you are ready to re-open and wanting to service them.
Within 2 – 3 weeks you should have an idea who is coming back and who isn’t then maybe you could personally reach out and offer some form of assistance (deferred payment for those impacted).
What you do in looking after other peoples animals so they can take care of their other priorities is important so provided your customers are happy with your previous services, have the financial means and the need then you should get them back at fair (not discounted) market rates.
Hope that helps…best of luck!