Baby's first birthday party- would the parents expext a full meal

I'd buy a meal for the children. Nuggets and chips being customary. Then the adults can order and pay for their own off the menu if they're hungry (disclaimer my kids are in their 20s so it probably not nuggets and chips anymore).

If it is around a meal time, I would put out enough that adults are not left hovering and hungry, but I do not think a first birthday means everyone expects a full plated meal.

A shared platter, cake, drinks and a few easy bits for the children is usually enough, especially if people know it is a play session rather than a sit-down party. At one, most people are there to celebrate you all getting through the first year, not to be formally hosted.

If you want one thing that makes it feel special without adding loads of faff, I would do one tiny keepable thing rather than more food or decor: a card or notebook where people write one line to your child, plus one dated note from you about what they are like right now. That tends to be the bit you actually value later.

It depends what time of day it as as to what amount of food generally- if it's a t lunchtime might need more food, but I don't think you usually need to provide a whole meal for adults at a first birthday.

You said "of course" you would buy food but I've never actually come across this set up. My advice is book it in the middle of the afternoon and get some bowls of nachos or chips to share, that kind of thing. Get them drinks too. Some places will sell thermos jugs of filter coffee and tea for parties.

Generally feeding parents varies by area, but 1st birthdays are a bit different anyway as the parents are more involved than the babies really. You wouldn't want 8 adults all politely sitting round through a mealtime getting hungry, but equally they are probably not expecting all to be fed burger and chips.