It's certainly a good plan. Lots of people want great wedding speeches, eulogies and lots more, but know that they don't have a good way with words - so they're happy to outsource it to somebody who does.
It may well not be feasible, depending on what childcare options you have - although maybe one to consider when they're older - but are you also any good with reading/presenting in public? If so, this is pretty much what a wedding/funeral/other celebrant does: speaks to you to draw out all of your personal thoughts, memories and important facts and interests and then draws it together into a beautifully compiled, special piece of lyrical art.
You may even find somebody who is amazing at composing music but rubbish with lyrics, so you could possibly collaborate.
I agree with PPs about prices, though. I get that it can feel awkward setting a price when it's your own personal skill and creations that you're selling, but it is for the best overall, so that everybody knows where they stand.
Otherwise, people can worry about giving you too little; or about paying way over the odds. Also, you will get nasty people who see it as their opportunity to royally rip you off and, even if they love it dearly, will still tell you it's only worth 50p to them, just because they're horrible and figure that they can get away with it.
Even if you feel uncomfortable doing so, you don't want to sell yourself short/inadvertently invite CFs, but you also don't want to deter genuine customers on a reasonable budget who just assume that such a bespoke service would be well out of their price-range, when it absolutely wouldn't. I would at least give a clear ball-park price, even if you're subsequently open to negotiations.
I would also provide people with a few samples of your work, so they know how good you are before they commit. They will want to trust that you're not the wordsmith equivalent of the people who go on the X-Factor, so confident of their vocal greatness, and then just tunelessly howl into the mic - and won't want to pay good money to hire somebody who produces even worse results than they could have done themselves!