Pumpkin Ale suggestions sought

I've never made a pumpkin ale but my wife loves Starbucks seasonal pumpkin coffee so I thought I'd give it a try. I have a good supply of Golden Promise and Vienna malt on hand. Will those malts make a good base for pumpkin ale?

Also, tell me if this sounds about right... I plan to add 3 to 4 pounds of pumpkin late in the boil. I've heard that you can use pumpkin in the mash but I have also heard that doing so is a good way to get a stuck mash.

I plan to add a spice extract of vanilla, allspice, nutmeg, cloves and cinnamon either in a secondary step or directly to the keg so I can adjust to taste.

Finally, how does adding some lactose sugar sound?

I do pumpkin in both the mash and boil, but I BIAB so no worries about a stuck mash.  I do pumpkin spice at flameout and in the fermenter.  I've never tried lactose, so not sure how that would work.  Sounds like you have a good plan going

How does using pumpkin in the BIAB work out? It doesn't just turn into a goo that squishes out of the bag? Also, how do you chill? I have a plate chiller and worry about gumming up the works.

Thanks,
Kevin

I put the pumpkin in a paint strainer bag, so no excess goop.  I have an immersion chiller, so not sure what would happen to a plate chiller

Don't waste your time with the pumpkin. Very little of that flavor comes through and is a pain if you are using a fresh pumpkin. Starbucks used to use real pumpkin in their lattes but people didn't like it. Now they stick to just the spices of a pumpkin pie. Really, that's all people are going for. Pumpkin itself doesn't really taste great, it's just a conduit to all that sugar and spice!

Nutmeg, allspice, cinnamon, ginger, cloves...Things in a pumpkin pie basically!

Thanks for the help. I think I'm going to bypass using actual pumpkin. It just sounds like a lot of headache for very little return.