My husband will be working in Amsterdam from mid-June to the end of September. Myself and the boys (ages: two years and three months) will mostly likely be with him for only a portion of the time (mid-June to the first week of August). I'm looking for ideas of weekend trips inside and outside of the Netherlands as well as fun things to do through the week with the kids. Thank you!
Find the park nearest where you are staying so your older one has a place to play and meet other kids. You will likely meet other moms while you tend the infant and can maybe get ideas from them on manageable trips with your little ones.
Does your husbands employer routinely send staff to Amsterdam? Perhaps the HR or travel dept can help with ideas, or put you in touch with other families that have had an assignment there and pick their brains?
I agree with the Park statement especially as Amsterdam has some lovely parks. Do you know where you are staying yet? The Vondelpark is very nice for children to run and play, to ride your bikes around or walk, to picnic, and just have a different feel from the city feeling. Westerpark is a personal favorite of mine too especially because it's near the islands which feel like a whole different world than the city center but they are only moments walking from the center. Another good place to let them play, meet other moms, and both parks are surrounded by neighborhoods with beautiful architecture, many shops, things to eat, cafes, etc. In fact, 1 of the islands has a children's petting zoo open during the day at certain times of year. They can see rabbits and other cute soft things.
Another fun zoo to take children to is the goat farm in the Amsterdam forest: http://www.geitenboerderij.nl/en/
The city zoo is Artis and a good family activity and I also believe many of the animals housed in the zoo are rescued from smugglers etc.
I found a link to child friendly cafes, and of course there are many more than this but some recommended ones: http://www.iamsterdam.com/en/visiting/what-to-do/families-and-children/10-child-friendly-restaurants-and-cafes
The 2 year old is old enough to visually appreciate boat rides and the Ij ferries in back of Centraal Station are all free and offer nice city views. It is a way to get the boat experience without paying for a canal tour with children so young yet at least one of them will still get a boat ride they can enjoy.
Your local playgrounds will usually be full of moms in the daytime too especially since you are there in summer.
Trips outside of Amsterdam-Maastricht is a very nice town and very pretty. Because of its position in the Southeast of the country the food has its own distinct flavour and foreign influences and it's a place to go and enjoy different architecture styles, small town life, and a lot of eating.
On a highspeed train Paris can be a quick weekend trip away and you can find cheap lodging deals there if you look well and ahead of time. If I'm correct the highspeed train tickets are much cheaper if you can manage to buy them weeks in advance of your trip.
Antwerp, Brussels, and Strasbourg are all things that can be done at a weekend as well and well connected to Amsterdam by train. Koln is a beautiful city that can be reached by train and enjoyed for a weekend as well. It is worth seeing even if only for its amazing cathedral.
And then there are beaches not far from Amsterdam with different qualities and at this time of year you're going you should make time to visit at least one: http://www.iamsterdam.com/en/visiting/areas/city-escapes/amsterdam-beach/amsterdam-beach-guide
That should be a good start to keep your family busy in and around town in child friendly ways!