First, you don't want vinyl. I don't like it either. My house has aluminium siding, which looks the same but doesn't at the same time. Would that be acceptable? Might also be cheaper than the wood, would require less ongoing maintenance. And my house has the original siding underneath, in whatever condition it might be in, including whatever lead paint is on it.
Second, roof. Multiple quotes is the best you can do, and old house research so you're knowledgeable.
Third, lead paint. Lead paint is primarily a danger if you're ingesting it. Little kids are of course prone to eating everything in sight. But since you don't plan to sand, just remove the siding, then some basic precautions should help a lot and be low cost.
-Ship the child (and the pregnant woman if possible, not sure if that's you or not) off to grandma's or somewhere else so they are out of the way during the work. Just makes everything easier.
-Close up the house as much as possible. Windows, doors, etc. Goal being to keep dust from getting in. Be very careful about going in or out of the house to minimize as well. Walk in, take your shoes off. Good idea regardless, will keep the house cleaner.
-And have them put plastic down outside to catch everything. Get the thicker plastic so it is more tear resistant. It'll help with general cleanup, but it'll also catch lead chips. When the work is done, roll it all up and toss it.
Fourth, paying for it. You're bad at saving cash. I get it, some people are. Does your employer allow you to have multiple accounts for direct deposit? If so, open an online savings account or something and divert some there, upfront. You never see it. But really, somethings you can't really put off and just have to figure out. (I have to do my roof, not that I want to.) So if you need to take out a loan, optimize it. Get the lowest interest rate, try to pay it off early, etc. Cash flow what you can of course.