Coming from someone myself who was 14 when I met my DP who was 16 (1 school year apart), I spent A LOT of time at his family home. I would go most evenings for dinner after school and would spend the whole weekend there. I didn’t by any means have a terrible family home, but my DP’s family home was so comforting and I was treated as one of their own. Nothing was ever too much and they were happy to see their DS happy.
DP’s family didn’t have a lot of spare monies and each meal I had was always delicious, nutritious and simple - given they probably felt the strain of feeding somebody else. It wasn’t fillet steak, caviar or any expensive meals at all. I conscientiously didn’t want to overstay my welcome at any time, but I was always offered dinner. If there was an occasion where I wasn’t, I would simply go home which was absolutely fine.
We would both offer to cook for the family which was great as we learned how to cook and as my DP had a weekend job it allowed him to pay for some groceries too.
My (now) MIL to-be would drop me home every single night out of choice, not because I had asked or had no other means of travelling, it’s just what she wanted to do.
When I turned 16 and found an apprenticeship, I moved into DP’s family home, where we lived for 7 years until we purchased our own house together. This in itself was such a blessing as his family willingly allowed us to save as much as we could so that we could purchase our first home.
I understand 14 and 16 sounds extremely young. But they are probably very mature for their age, as I was myself.
I have always and will always be SO grateful DP’s family. Without them, I truly wouldn’t be where I am today. They have given me more support than my own family ever have.
12 years on, we have bought a house and are getting married next year.
Ultimately, the bottom line is is would you like DS to be happy? 1 extra mouth to feed a few nights per week can be accommodated for easily. But boundaries are always important. My FIL to-be set boundaries from very early on - I was welcome any time but I was never allowed
to sleep over in the same room (due to my age) which is of course absolutely fair enough and it was his home and the boundaries were respected.
If the issues is having an extra mouth to feed then perhaps suggest that she comes certain nights per week only? Could you suggest that perhaps DS could go to her family home for dinner too? If there’s a further underlying issue then you also need to address that. But I think your DS would appreciate nothing more than your support (which you obviously do give which I’m sure he is very grateful for) but asking to cut down on visits because of meals doesn’t seem justifiable imo.
Hope this helps :)