It was mine and DH's anniversary on sunday. We want to go out for a meal and LO (5 weeks old) would be coming with us. MIL thinks people will give us funny looks being out in the evening (we will be finished by 8 at the latest) with a baby. He's too young to be able to tell night from day, and he sleeps wonderfully in his pram, so it's not an ishoo really, but I fear being JUDGED by others (yes I am pathetic enough for it to bother me). Would you sack off the meal? Is it a bit too late to be keeping an infant out? I can understand if it's a toddler with a set bedtime out quite late, but he sleeps whenever, so I really don't see the problem. I am, however, new to this baby malarkey, so am willing to be told I'm wrong.
DD is now 6 months and she has been to many restaurants and pubs (!) with us. She normally fell asleep on the way there and slept through the meal/drink and then we'd put her to bed when she got home. Unfortunately she's getting a bit too alert for this trick these days but we certainly didn't have a problem taking her out and about with us when she was younger. I say go for it and enjoy yourselves!
GO! And stay as late as you feel like. If you have a baby that will sleep in car seat/pushchair by the table or in the corner then you are very lucky and nobody in their right mind will have a problem with it! Make the most of it because as you say, at toddler age it becomes impossible.
I also don't think there is a "late" for a 5 weeks old baby. Often their sleeping patterns aren't settled at that age, or they might still be awake at 9 or 10 (or 11 in the case of my first child ) or sleep from 7 to 2 and then stay awake for hrs!!! .