I remember reading a children's book in the 1970s/1980s about a family with their own spaceship exploring new planets. I believe there were 2 parents, 2 children, and a dog-like pet. The main plot point was that their spaceship had become disabled somehow (crashed or run out of fuel), and they were able to find seedpods that contained lighter than air gas to attach to their spaceship to allow it to fly again, at least temporarily.
As confirmed by the asker, the book is Brian Earnshaw's Dragonfall 5 and the Royal Beast, the second in a children's sci-fi book series originally published in the UK in 1972 (and in the US in 1975).
The Dragonfall 5 series features a spacefaring family of 4 (2 adults and 2 kids) with a flying dog, and their adventures transporting passengers and cargo through space.
The book's summary on the Wikipedia series page reads:
Transporting a valuable and rare animal "The Royal Beast", the crew of Dragonfall 5 set down on a lush forest world to re-stock on food. However the natives have their eyes on the cargo...
On its Goodreads page, you can see the floating seedpods in the background of the cover art.