@Sean1204
I host long term guests (people staying a few weeks or months) so I have found this works well for some of them, but I am not sure it's worth it for people staying just a few days. It depends on what the offer is.
I had vouchers to offer a few free boxes with Hellofresh and one of my guests used this but decided not to sign up. Another guest did end up ordering a couple of other boxes. I also had discount vouchers for a one month subscription which a couple who stayed took up.
The problem is, none of these referrals rewarded me at all! When I asked Hellofresh about it, they said you only get credit when you send a specific referral link (not the vouchers they had sent me). Just something to be aware about. I am sure different companies operate in different ways, but just double check the small print.
I think it's important not to be pushy about these things. Firstly, think about is it good value to the guest. I would only suggest this to guests who seem to like to cook most of their own meals and are staying long enough to take advantage of the offer. I would also explain to them clearly that they need to cancel their subscription in advance so that they don't lose money.
If you do a house tour on check in, or a local guide with info about supermarkets, eating out etc. these are good places to mention that you can offer a discount. Or, you might have a house manual and could mention it there, telling guests to let you know if they are interested. It's best not to be too pushy about these things.