Dog being over protective, advice please

[Montyforever]

Im sure a few of you will remember Barney the crazy greyhound hes always been a complete sweet heart and he still is of course. But recently my mum has had a baby and hes become very over protective of not only baby (when outside/strangers) but also my younger cousins.
Hes never bitten anyone, but has started lunging and growling at other dogs/strangers that get too close to "his" kids when we are out and about. Hes been his usual happy friendly self with midwives/health visitors/friends/ relatives visiting and has taken everything in his stride despite it all being very unsettling. Weve had lots of new dogs in the block too (shared garden) and there have been a few fights which has upset him as hes heard them although hes not been involved. One of the new dogs feels the need to constantly jump up at Barney and hes understandably growled a few times but he never snaps and we try to avoid them being out there together. But im sure that it hasnt helped with the guarding issue
so any tips to avoid this escalating? Hes his normal happy self most of the time but becomes really overprotective when out with the kids which is shocking really as hes usually a hide behind your legs type

 

[CorvusCorax]

This is just an idea, as I cannot see the dog in front of me.

He might feel 'elevated' into this position by the recent upheaval, which could be very stressful for him so you need to be vigilant and you need to take the position that he may be thinking he has been forced into.

So for instance you could use your body to block him from approaching people, use his lead to keep him behind you, so you literally 'step up' and say, no, it's OK, I'll handle this, you chill out.
Don't allow him to get to the stage where he is lunging and growling, because you are thinking ahead and using your body or your lead to physically prevent him from doing so and making him feel more stable and secure.

You might also want to pop him to the vets to rule out a physical cause if the behaviour is very sudden and out of character.