This has been covered a number of times before on these forums.  My most recent experience was £10 a month for each, which was regarded as derisory by the recipients.

Last place I worked paid £25 per month for first aiders. We also promoted this as a life skill that they could take with them anywhere and would also benefit them and their friends and family.

Fo fire Wardens we didn't offer money but we made this a training requirement for supervisors and team leaders as these were the people that staff would look to in the event of something like a fire alarm activation anyway, so it was an expected part of the role.

However, what worked there doesn work in my new company and may not suit yours either.

Seen the range from Union agreed pence per hour uplift to wage rates through monthly sums to an annual once a year payment.

Some times money is not the best reward as it can cause salary to cross a threshold increasing tax liability (and wiping out the benefit).