I have some ideas now....

Visit vinnies and/or salvos (or similar) and scour them for supplies. You should be able to pick up:
• mismatched teacups, saucers and plates (very grown up but won’t cost the earth)
• teaspoons
• tablecloths/doilies for the table
• “real” napkins
• servingware – for finger sandwiches, small cakes etc
• a couple of teapots
You can either make or buy some crepe paper lanterns (I think most $2 shops have these) to hang from the ceiling. You can also buy the led tealights to put on the table. My mum uses these and they’re really effective and no one gets burnt.

Just decorate “old lady-ish” lots of floral with hues of pinks, yellows and lavender.

You could even ask the girls to wear a fancy hat.

There are a few games that you could play around the table, pass the parcel? What if they do something crafty after they have eaten? They could make some cards or something that they could then take home with them for example a paper party broach, bracelets or paper hats? Origami finger puppets? You can get the kits (again from the $2 shops or spotlight or similar).