Regarding the birdhouse, besides "calling the birds" and "feeding the birds" there is an event that can happen if you have both the bird house and the bird bath repaired. I won't say what the event is as that might spoil it for you, but having both can trigger an event -- although it has only happened in one house for me and I have both in several now.
Regarding the bbq, on another thread where people were talking about young kids being orphaned, someone said that if they have a bbq that they can eat using that. Hasn't yet happened to me so I don't know, but just to be on the safe side I did just buy the bbq for a couple where the father is 63 and the mother is 58 and they have an 8 year old biological son and an 8 year old adopted son. I don't want to open my game and find them both dead and the boys still too young to cook, so I got the bbq just in case.
I haven't yet bought the lawn chairs and was wondering whether they could "nap" in them or not. I do buy the hammock though for all my households -- a holdover from when we were still having sleeping problems in the earlier versions.
eta -- Hi Lewanda! I checked back on this thread and saw your post but also saw that someone else had already posted the answer. I just got done putting your new head mods into my game, haven't gone in yet to see what they look like, but I'm sure I'll love them as I love all your other stuff. Hate to admit it, Lewanda, but I don't know how to hide spoilers.
That's the main reason I didn't want to put it into my post.