Would I allow it?
It depends.
There are some risks attached to the walk, there are some benefits.
Q1. DESIRE.
Do you WANT your DD to do this walk? Does she?
If either of you feel uncomfortable, then don’t do it. It’s all very well to talk about independence being good for mental health, but if it makes either of you scared or anxious, then that’s not helping your mental health. There are benefits for mental health in being independent in small increments, but there are also benefits to mental health in having a lovely walk with your dad and sibling before you start your day!
Q2. NECESSITY.
Is it really necessary?
If you were a single mum and asked the same q because this was the ‘only’ way you could manage the school run and still get to work on time, I’d say to go for it!
But, from your OP, it doesn’t sound really ‘necessary’ for your DD to walk alone but instead just something your DH wants to do, is that right? I’m guessing your DH probably could walk the extra few mins if he had to ( even if he had to carry the toddler)? So it’s truly just a matter of choice.
It’s also absolutely not necessary to walk to school at age 8 for your daughter to learn independence. There’s plenty of time for her to learn this skill, at a pace that suits the whole family. Plenty of people don’t walk to school alone at age 8 and easily adjust to it just a year or two later. There are also loads of ways of learning independence; this is just one of them.
Q3. PARENTING STYLE
It’s totally down to your parenting style if you think this is ok. It’s ok if you allow it; it’s ok if you don’t. It’s also ok to say ‘not yet’ while you think about it more, or propose a compromise such as your DH walking another 3 mins rather than 6 so your DD only walks an even smaller distance!
Finally it’s absolutely NOT coddling nor anxiety to delay this step; we’re not talking about a teenager here.
Good luck with your decision!