Keep it simple, Stupid.
It has been my experience that parents often want so badly to reward their children. So badly that they will make plans (for when they can afford it) to take them to a child friendly restaurant or save to buy them a gaming system. I encourage parents to give what they can today. Draw a smiley face on a chart, give a sticker, give a hug, play a game, go for a walk, invite them to make dinner with you. Anything that means more of your time and attention is a PERFECT reward for them.
Side note: Learned to replace the words crap, stupid, shoot, and dang with more appropriate, kid friendly terms such as crikey, silly, shootin’hoops, and diggitydog. I still mess up all of the time. The kids usually let me know with a snicker, smile or by repeating it 5 times when their parents come back into the session. Roll with it!